Recently bought a Sena Outrush modular from Fortnine, and have had a Scorpion EVO modular for a number of years (no built in comms but I added a Cardo). Haven't ridden with the Sena yet so no comment, generally modulars are a bit noisier than full faced but easier to put on.
Helmet venting does help in the heat (if you are moving obviously). I never ride with the chin bar up, don't think it would be a good idea at speed. The Scorpion chin bar is removeable and becomes a 3/4, I do ride that way in hot weather sometimes. Number one importance is fit & comfort, oh and modulars are a bit heavier too, if that is important to you.
PS Welcome to the site!