Another congrats to your recent success, it isnt easy to consistently FT alot of MTTs - let alone win several of them.
Now, onto the pocket pairs...for me "small" pairs are 66 and less, mid pairs are 77-TT and high pairs are JJ+. This is my own personal strategy so take it for what it is.
A good rule of thumb when going to the flop with a "speculative hand" - whether it be a pocket pair or suited connector - is to not risk more than 10% of your stack to do so. If you have 8k on the BTN and someone makes a huge open to 3k and you have 55s - its probably a good idea to just fold and move on - its a huge chunk of our stack and really all we are looking to do is set mine here and there are not a ton of good flops coming for our tiny little 5's so it is an all around a terrible play to call. If we are playing this hand in this example at all it should be All In or fold - me personally, I would fold unless I knew for a fact my opponent was opening any 2 cards and I was willing to flip.
Small pairs out of position/early position - I usually fold these from UTG seats at a full 9 or 8 handed table. You could argue for a limp - call strategy, but this turns your hand face up when you raise someone post flop or tend to call on very dry unconnected boards so for me, if i cant open the hand, I fold and move on. As iterated in the example above - there are not going to be a ton of good flops for pairs 66 and under - so no sense committing unnecessary chips into the pot if we don't have to. That being said, with a healthy stack and from late position - I am always opening small pairs.
Mid pairs I will open sometimes from early positions, sometimes I will limp call with them and sometimes I will fold 77 or 88 - 99 or TT from UTG, I generally suck it up and open. Anyhow, UTG at a 9 handed table with a middling stack if I go opening 88, there aren't going to be a high number of flops I am comfortable with and if I were to get 3bet preflop then I am going to be in a spot where I will be very uncomfortable making any decision other than folding. If we commit and see the flop and it comes down K J 4 - then what are we going to do? Especially if we are out of position? It just leads to a huge mess so early position and mid pairs should be approached with caution.
I am always opening middle pairs in middle and late table positions. They can generally be played accordingly and pretty profitably post flop especially if you have position - keep in mind even when we are in later position we still don't want to get 3bet while holding a mid range pair.
Big pairs - pretty standard, we open these pairs all the time from all positions and if we get 3bet we are usually comfortable calling if not putting in the cold 4bet. These are the easiest pairs to play so I don't think there is much use to dive into a ton of detail.
One more comment - an earlier reply said they were "3 betting all pairs 77+ in position" - I do not like this line and do not agree with this at all. Yes - we need to balance our range and should not only be 3 betting AA, KK, QQ, AK, JJ, etc - so maybe we can do this once in a while in situations where our stack size allows us to put pressure on our opponents and make moves like this. The problem with sticking to this logic religiously is that if you are constantly 3 betting mid pairs it opens the door to a huge list of problems.
Say we do 3 bet 77, 88 ,99 or even TT - and then we get hit with a huge 4 bet or the opponent just jams on us...well now what? When do we call off? What are they shoving/4 betting us with - do we beat that shove/4bet range? Lots of problems open up and we can easily answer these when we are holding premium pairs so the decision isn't anywhere near as difficult or crucial.
The other side is they just cold call the 3 bet - well now heading to the flop with 99 or less - how many boards are going to be safe for us? What could our opponents call a 3 bet with? Does that connect with the flop? Do we beat their 3bet calling range on the flop? I have made this mistake 100000 times over the course my online play and it took a while but I did eventually learn -- say we do have 99, we 3 bet, an opponent calls and the flop comes out::
K 4 8 - our opponent checks so we decide to cbet this board - then we get check raised and our opponent goes all in - we cover them well enough and it costs us roughly 35% (or less) of our stack to make the call, so we do and they show up with KQ, KJ, KT, etc...one over card on the board and they slammed it. How many times have you seen this happen? Too much, right? Well we avoid this by checking back flop - the turn comes a brick we can call a turn bet - and if they make a reasonable river bet we can probably call that too - we still lose the hand, but we lose a lot less chips in the end playing it this way. We achieve roughly the same result by just calling their open preflop and NOT 3 betting them - the flop comes the same, they cbet - we call, then we can evaluate the turns and rivers as they come and we are not over committed. Make sense?
I hope this insight helps out and improves your play in some shape or form. Thanks for reading.