I am a small-winning microstakes nlhe player and would like to improve my understanding of the game, I have read the modern poker theory book so have some understanding of game theory but I have very little experience with solvers.

I recently saw a video where someone mentioned studying the solutions for a subset of flops (about 100+), using the daily free gtow solve (if only have the free version) and build heuristics. Is this a good use of time? Also how useful is this if I don't know how to deviate from them.

For example
SB v BB SRP
flop 2cQsTs

An observation I made is that SB more frequently cbets combos with a spade than those without. Looking at BB I can see they 3b more with hands that have a spade, so I would think the reason SB bets with spade is because less chance you will get 3bet, but also because you have more equity. Is that accurate? What is the balance between these factors? are there other factors?

So based on that I was thinking most micros players won't be 3betting as much as the chart shows from BB but how would you calculate how to adjust to that (if you dont have a full solver), and is that calculation something that could be applied to other spots?

That's definitely a good way to dip your toes in the water. You can also try a free postflop solver. Studying GTO is useful even without exploiting, because you presumably haven't built up a solid baseline strategy yet.

subsets are totaly the way to go for micros. 100+ flops covers the main board types so u can build solid heuristics. Even if u dont deviate perfectly, knowin the baseline lets u spot when ppl mess up. On QsTs2c, SB smashes it cuz BB lacks AK/QQ/TT preflop. Holding a spade blocks there check-raises and boosts ur equity big time. Blockers are huge on flushy boards cuz they prevent villain from goin agro. If BB isnt raising enough, u should basicly cbet way more often. U get to see turns cheap and realize equity with weak pairs or draws. Adjust by betting thin value hands u might normaly check in a solver. This applies anywere: if they dont raise, u get to bully em with bets!

thank you that's very clear.

At microstakes the answer is almost always exploit over GTO. Your opponents are making such massive mistakes that a balanced strategy leaves money on the table. The way I think about it - use GTO as your baseline to understand what correct play looks like, then deviate from it whenever you see a clear population tendency. At micros the biggest exploits are usually sizing up your value bets because people call too much, and cutting your bluff frequency because people dont fold enough.