While playing weekend tournaments at a local casino, I’ve noticed a few tendencies in the player pool.

In the mid stages, once BB ante comes into play:
Many players open quite big (3–5bb) from EP/MP, even at 20–30bb stacks. This is likely due to the BB ante as dead money and/or trying to avoid multiway pots.
Some players call short-stack shoves quite wide. For example, yesterday I shoved 12bb from the BTN with KTo and got called by the SB with QJo.

In the early stages (no ante and re-entry still possible), ranges seem even wider. E.g., there was a hand where MP opened to 3bb , I shoved 18bb from the BTN with AK, and MP snap-called me with 44.

My question is what adjustments I should take given these tendencies:

Should I tighten my opening and shoving ranges?
How should I adjust vs 4–5bb open raises?
Should I change my own opening sizes from EP/MP (I currently use standard 2–2.5bb) once BB ante in play?

Thanks in advance, and apologies if some of these questions are basic.

I think it is important to know what the buy in amounts are in these local weekend tournaments. The smaller the buy in, the more it makes sense that people are playing that badly. Also, it is likely that it is being done by people who want to double up or buy back in. So in these situations (which also happens at WSOP Circuit events) I make sure to get it in when I have good hands where I am making polarizing bets which could considered either monsters or bluffs.

I play live tournaments only for the past 15 years or so and even before then only played online at WPT to get used to final table dynamics with less than 6 players. I have very rarely seen any players opening at greater than 3 bb's. It has happened basically twice where players were doing it regularly. The first time was an Asian guy latish in a tournament (I think we were in the money already) and he was raising at 5x every time preflop. I had KK and went all in with 17 bb's if I remember correctly and he couldn't fold and called with like A7o and won the hand. The other time was a Russian woman who was chip leader when we were down to 3 players and she started opening at 4x and 5x when on the BTN. It basically cost her the tournament because when the short stack jammed she had to call for like 13 bb's. She also folded twice to my 3-bet jams previously because I was second in chips and she probably was raising that large to encourage folds.

When players who typically open > 3x preflop it is because they have JJ most of the time. Lately its being done with AK as well sometimes. I have seen it with QQ and TT but infrequently. Often it is because they want to take down the hand preflop and not have to play OOP. But in general they open at 3x or 2.5x with other hands.

Most people tend to open 3x at the start of tournaments. Because we usually start with over 150 blinds. I have seen some people raise to 700 at 100/200 but not always. So my guess is they want to play a bigger pot with a decent hand. One time a guy opened to 1200 at 100/200 on several occasions. We never saw his hands but he won decent size pots with one or two preflop callers. He was a wild player who would go all in with draws frequently in very early stages so he could double up or buy back in. He wanted to dominate with large stacks.

The only casino where I have ever seen crazy wild opening sequences where 3 bets were like 5x and 4 bet jams with like >100 blinds was in the Orleans in Las Vegas. It was a cheapish ($300? or $400?) tournament with multiple day 1's and a very large guarantee (like $500k?). People wanted to double up or buy back in. I had bought back in and had like 40 blinds when a woman opened to 3x UTG call call call and I jammed in the BB with AKo because my normal 3-bet size would have been 18 bb's which was close to my 50% of my stack. And I didn't want to play a huge pot OOP with AK. The woman called with QJs and of course won...

In the field you are describing where people are over raising and over calling jams with hands like 44 its a good situation to double up early or buy back in. But against large raises like 4x or 5x I would not be calling in the BB with most hands. I also would not be bluff squeezing in the SB or BB with any hands. I typically call with PP's vs EP raises but here the problem is we have to take into consideration that we won't be able to call any large flop bets with overcards so I likely would be folding smallish PP's a lot more.

I absolutely would not tighten my opening and shoving ranges. In fact the advantage I have is that I always shove hands like AA/KK when I am in my raise and 3-bet shoving ranges. And I get called a lot because people generally think that with hands like AA and KK I would raise smaller so I would get called more.

I also would not change my opening raise sizes when other people are raising large. But I will often fold to overly large 3-bets (when I don't have a really nice hand) because people do that hoping to get it all in with monsters. I also don't start limping first in preflop when a lot of players are limping preflop.

I think that if players are calling jams with small PP's that means I will likely start 3-bet jamming with hands like 88/77/66 and even 55 against them.

It’s a €100 tournament (I realize that might be considered low stakes for some) with 20-minute levels and a single re-entry during the first 2 hours. It usually gets around 30–35 players. Payout structure is top-heavy (4–5 paid places).
Not the best structure overall, but unfortunately I don’t have many other options to play nearby where I live.

I wouldn't necessarily tighten up your opening and shoving ranges. If you jam with KT and get called by QJ that's a good result for you. You will double up 60% of the time.

However, when someone raises to 5x first in, then you want to play tighter and also 3-bet more/ call less compared to if they were opening to a smaller size. That's kind of common sense. As more money goes in your range gets tighter, similarly to how you would call with a tighter range on the flop facing a pot-sized bet compared to if you were facing a 1/4 pot bet.

Against their big bets you want to play a strong range and play it aggressively. The worst thing to do is call a lot with speculative hands, then fold whenever you miss the flop (the way recreational players play). You'll just bleed chips that way.

Against players who are willing to put all their chips in with trashy hands, you actually should be somewhat looser with the range that is willing to call an all in. Don't play as crazy as them, but for example let's say the worst hand you would normally call an all in with in a certain spot is AQ. You might call an all in with AJ or even AT if you know your opponent is going all in with lots of weak hands they shouldn't be shoving with. You want to adjust to your opponent.

Anyway there's a lot more nuance to it than that, but I hope this helps!