Looking for advice for preparing to CC

Hey folks, I am not new to OWB carry but now with my CCW I will be carrying 95% of the time IWB. I have got 2 preferred weapons for my EDC. A Ruger SR9C and a Taurus PT111 Gen 2, I could never get a BP9CC and then I just finished filling out the paperwork and purchased the Taurus and they get a delivery and what is in it? Yep a BP, too late . I have an Alien Gear holster for the Ruger and I have coming a new Theis EZ Clip Holster from Tommy Theis, and I have a Tagua IPH holster for both plus a snug fit thru the belt open carry and thumb lock carry for OWB. I also have an awesome n82tactical holster from Nate x 2 that will handle all of my S&Ws and I can carry a fullsize M&P with hardly any footprint. My question is this. I have just ordered a Jake Belt from Tommy Theis and ordered it slightly larger than my pants size per his advice. Now I wear between a 38 and 40 inch waist on casual pants and 40" in jeans. Do I need to go out and buy 42" jeans now and step up in casual pants? What adjustments do you need to make because, when I am not carrying, bigger pants and the belt would fall off. I know it seems like a silly question. My OWB holsters require nothing and the foot print is nothing. I can wear a Tshirt and wear a fullsize M&P and you would barely make it out. It is IWB I am concerned with. Oh yeah I had Theis change my order to the EZ Clip instead of his old trustworthy 2 clip rig and he was kind enough to do so, so in return I will write a review on it. Any thoughts? Your advice would greatly be appreciated, and I mean from the simplest of things, from putting it on to whatever, I intend to carry at between 3:00 & 5:00. I also will be driving alot too. Oh yeah, not out of the Bersa want list but will be probably looking for a full size when I build up the funds.
Thanks folks,
Michael