I did my standard kropki/arrow start - fill in the possibles for black dots, single digit arrows of 3+ (none in this case), and double-digit arrows. It was easy to determine the 4 cells of double-digit arrows are (from top to bottom) 1/2, 3-9 (1/2 used up in column), 3/4 (1/2 used up in column), 1/2.

Since one of the Region2/Region5 arrows must be 23 or 24, it contains a 8 and 9, and either 6 or 7. I'll use Region2 for the explanation... If the Region2 arrow is 23 or 24 and contains 8/9, the only place 8/9 can go in Region3 is C9 not in arrow sum, and the 6 or 7 in C8 on the arrow. Now, since 8/9 can't be the Region3 sum, 7 can't be on its arrow... so it must be the 6 (making the Region2 arrow 23) with a 1 to make a 7 sum. Similarly, all this applies to Region5/Region6 as well.

So, 1 of the bigger arrows is 23 with 6/8/9, and the corresponding smaller arrow is 7 with 6/1. That means the other smaller arrow sum is 3/4/5/6, and its arrow can't contain a 1. That means it is either 5 with 2/3 or 6 with 2/4. Either way, there must be 2. That means in Region9, the 1 and 2 must go in C9, on the arrow, making its sum 3.

Now, look at Region3. If the big arrow sum is 23, then the small arrow is 1/6 (sum 7) and C9 is 8/9. And since that means the other big arrow is 41/14, the 4 in Region3 goes in R3C8. But, then where does 4 go in Region9? Nowhere. Therefore, the Region3 big arrow cannot be 23, so it is 1x. That makes Region6 arrow the 32/23. Things start falling into place from there.

I like near the end of the solve, on the large 32 arrow, you're left with:

4/5/7
5/7/8
6
4/5
7
2

So if you make the 4/5 a 4, the others must be 5 and 8. But, R9C8 cell is 4/5/8 and sees all 3, so the 4/5 can't be 4.

It was SET based, from the columns and rows containing the arrows.

I just tried to do it that way but didn't get anywhere. I'm clearly not seeing what I should be.

A normal arrow with a single cell total will have its arrow cancel its circle.
A double cell total will leave a difference of 9, 18 , 27, ... Counting correctly will leave you with the leftmost 6 cells of R34 being 1,2,3 times two, and the bottom 3 cells of C9 also being 1,2,3.

Might've gotten lucky that I saw the trick to sort out the arrows in boxes 2 and 8 immediately

I lost sight of the fact that the upper left arrow was also a thermometer. I was stuck a good 15 mins and wound up bifercating a few moves in frustration, which revealed the thermometer when it errored. Quite the dope slap!

The middle is key obv

in the corners you have 6789 and 1 in the middle with a 2345 cross. The 9 has to be lower right in the middle sector. I got the biggest boost from focussing on the sector 3 and 6, and what numbers could and could not be in play to get to 9 in sector 6. And what could be used to get to 6, 7 or 8 in the lower left square of sector 3. 1 and 2 had to be in column 8 rows 123, and this helped determine that the 9 had to be a 234, and the 2 had to be middle right in sector 6.

After that everything fell together with enough info to complete.