Well duffy the purpose of the powder (in this case) is not to give any more coverage but to set your foundation or tinted moisturiser. In hot weather u sweat so much that it is absolutely essential to carry a powder (either pressed or loose) so that you can set your foundation/moist. and re-touch whenever its necessary.
But if ur wearing a moisturiser u could always re-apply that if it comes off… with a foundation it takes a little more effort to re-apply (and they’re expensive so u don’t really want to use them up unnecesarily) so its just easier to use the powder. I’ll leave it up to you whether u want to carry your moisturiser with you everywhere and re-apply when it starts coming off or just use a powder to re-touch.
I would go for Makeup forever’s High Definition loose powder:
Sephora: MAKE UP FOR EVER HD Microfinish Powder: Loose Powder
It looks white but don’t worry it goes on completely translucent.
For pressed powders… hmm u can use any good brand really. I am currently using Mac’s and it works fine. Or you could even buy one from pakistan, my mom has a pressed powder from pakistan (she got it for like 100 rupees or something) and that works perfectly fine too.