Breeding Guppies

I have a 29 gallon tank that I setup for guppies. I recently purchased some fish the other day (2 males 2 females) and I had a question regarding the fish. I am relatively accustomed to keeping livebearers as I’ve had swordtails and guppies in the past. I am well aware that unless I separate my guppies they will breed and my question is regarding female size regulations. The two females that I have are relatively small and I was wondering if I should be cautious about them breeding as they seem fairly small for breeding. I know that once they’ve reached sexual maturity that they are ready for breeding but I’m not opposed to separating the males to prevent this. I was also wondering how many guppies I can put in a 29 gal? Should I separate my guppies or am I being too cautious? I was considering buying some larger females when they are available or maybe buying only males.