Should I be going for a variable opening size strategy where I size my bets depending on my position ex: high bet sizing in early position and lower in later position. Or should I be using a fixed opening size strategy where I am using the same size to open regardless of the position and cards in my hand?

This is a cool question actually, as bet sizing is like one of the more interesting theory concept of Nl Holdem.

My approach is preflop, i adjust to table. For example my defult sizing preflop not knowing opponents online is 2.5x utg,mp, 2.2x co, 2x btn. And then i ajdust acorrding to situation, if i am in pasive game where there is a lot of calling, but not a lot of 3beting, im increasing sizing and tightening ranges a little, if its agro i stay the same, and if i find fish, i want to exploit when in blinds i switch to 3x ect. But basic is 2.5, 2.2 i 2x

Live i can go large, because usually people tend to call a ton with so i want to punish them, and i can even 5x, finding my self 6x sometimes. But depends on stacks, players and game.

id say variable betting. fixed betting is bad. have a opening hand strategy. but vary it up according to number of people at the table. type of players. and your winning or losing streak.

Depending on stack size I range between 2.2x to 2.6x

Think about what your bet is supposed to accomplish and then size accordingly. This may vary according to the table dynamic or who happens to be in the blinds (do they defend a lot? Do they fold easily?)

Fixed sizes are only good if you are worried that people may otherwise range you according to your hand (i.e. if you are prone to picking bet sizes based on the strength of your hand. Which obvisouy is a big no-no. )

always open to the same size, there are more important things to think about, in micros 3x in all positions is std, maybe less in btn, but do not change the size, especially ep-co for any reason, maybe you can open 3 in btn if there is a fish in the blinds or if the blinds 3b very little. also 3x sb, this does not change for any reason or the bb will defend more (do not change if you have AA xd) as I say there are more important things to think about, just always open to the same size

Live or online? I think it's more important to remain consistent online than live. But also important to be aware of what's 'accepting' to the table/players for the action you desire.

I play mainly 1/2 live and I vary my opening bets probably more than any Player you'll see and it does generate comments quite often. I open to 7, 11 or 16 from any position with my full range and will adjust based on how the table reacts. Although it's easy to think you need to 'protect' your stack by leaning towards larger opening bets after you build your stack, I think it's more important to try and keep the game 'small' and remain consistent unless 'all' the stacks have grown.

Where I'm more consistent (probably too much) is on the Flop where my bet sizing is basically geared towards the size of the pot. Then I go for value on the Turn based on the Player types remaining in the hand rather than pot size.

If the Players at the table don't change over (or they're just regs) and I get to show down lots of holdings due to my active style then the added mystery that AA (or 57o) can be opened for 'any' bet size contributes to my ability to gain value on the Turn and/or steal a higher percentage of pots on the Flop. GL

In 6max zoom games I open 3.5 UTG, 3 in MP/CO and 2.5 on the BTN. Obviously my range is wider on the button, but the value of 3bet bluffing me goes down.