general rule for pairs when stacks are deep: see a flop as cheaply as possible, try to hit a set, and stack off majority of the time. obviously some exceptions, depending on situation.
is it a smart play to go all-in with small pairs in an mtt? it would depend on the level of the mtt and your stack size.
if it's at the start and everyone has 100 bbs and you jam utg to win the pot of 1.5 bbs, then you're risking 100 bbs for a 1.5% increase. not only that, but if you're called and you have 44, then a lot of other pairs dominate you or you're in a flip situation for your mtt life. against decent players that might call off with 1010+, ak o/s, you're losing 31% of the time.
if it's in the later stages and/or you have less big blinds, then jamming might be a more favorable option. in the same scenario, lets say you have 8 bbs and you jam 33 utg. assuming no antes, you're risking 8 bbs to win 1.5 bbs for a ~19% chip increase. plus, your
equity to win increases even more because players are going to call you off much wider. lets say big stack calls of with 50% of
hands, then you're winning and doubling up ~50% of the time.
the difference is, is the risk worth the reward? risking your mtt life for 1.5% increase seems silly, especially since you have so much play ability with 100 bbs. at the same time risking an 8 bb mtt life for a 19% chip increase is much more worth it as you don't have as many options.
then there is playing pairs with short-middle stacks, like 15-35 bbs. and what you should do in different scenarios like what pairs you should just open fold from early position with 15-20 bbs, what pairs you can/should open from early position, what pairs you should call a raise with, 3bet with, or even 3bet jam with, etc. but these are more situational and are better answered with more information.
