Trizact is extremely expensive and honestly if I wasn't a professional, I would probably only buy mirka abralon. I went through 4 boxes of 6" Trizact 1500 & another 5 boxes of 6" Trizact 3000 grit in 2017 alone. I also went through several boxes of the 3" versions. I wouldn't be surprised if I spent $1,000 in Trizact sanding discs last year alone.
And yes, years ago when I first started wet sanding re-painted classic cars I wish I would have known about Mirka Abralon. Trizact 3000 grit is relatively easy to use and even if you're not experience with wet-sanding I think it'd be difficult to do too much damage. But, Trizact 1500 removes paint so rapidly that it's incredibly difficult to see through the slurry of material you create during the wet-sanding process, making it less than ideal for guys without much sanding experience.
As for the interface pad. I use either the 3" or 6" 3m interface pad for ALL my wet sanding. I even use it with Mirka Abralon discs which have a foam interface and for Trizact 3000 grit discs. The foam interface creates a much smoother and less aggressive sanding process.
Also, I know Mike has an article somewhere that talks about finding the sweet spot with the amount of water sprayed onto the panel when wet-sanding. He is completely accurate in suggesting only using a very light mist of water and refers to the process as damps sanding, otherwise the abrasive grit of the sanding disc will hydroplane over the surface and will reduce the bite of the sanding disc removing less material.
If you don't have a ton of experience with machine wet-sanding, not only should you absolutely use a foam interface BUT you should also spray more water on the surface, reducing the aggressiveness, at least until you are more comfortable.