I used the ones with poppers for DD1 until she was potty trained, then we went onto the ones without poppers. I wont put her in a vest on a hot day, but will probably keep her in vests in general until she is 8/9/10 sort of age when I guess she will progress onto crop tops, and then eventually bras... ah scary!!!
DD2 is still in the popper vest. I like them for keeping the nappy in place, so on a hot day, I will put her in a vest and shorts, rather than a t-shirt and shorts, but I buy vests that look more like a top for the summer, like this - https://www.jojomamanbebe.co.uk/sp+peter-pan-baby-bodysuits-in-multibuy-offers+d2795
Or I will put her in one of these sort of playsuits - https://www.jojomamanbebe.co.uk/sp+breton-stripe-baby-rompers-in-baby--multibuys+B2393
On a cold day, I will often wear a spaghetti type vest under my top and I'm 29! lol