In a few weeks we are about to receive our new 2019 Tige R21. As first-time wake boat owners we chose Tige based on a lot of research (many thanks and the good feeling with a local dealer.

I have a couple small projects planned when it arrives and could use some help, as I think I have exhausted the forum search.
I have a lot of experience with wiring race cars, but nothing with stereos (or really boats)....
Pertaining to my questions, for our build we opted for the R-ICE Power Premium Sound and the Electronic Isolator (Blue Sea?) and dual battery option.

We had separately purchased a new HTX-2 and pair of ICON-8s very cheap, which I would like to add.
What gauge wiring comes factory from battery switch to the existing HTX-6? Will I need to pull 1/0? Or will I just add distribution blocks to share the power?
Is the smartest decision to use a Wetsounds Amp Wiring kit, or are there other options (JL Marine)? I don't mine piecing together the right components instead of buying a kit.
I believe the TT2 is already setup for speaker zones, is this done through a separate set of RCA outputs? Or an amp control wire, and I must split the RCA? Are either of these existing and terminating in the port locker?
Given the time would you recommend building an amp rack to clean of the install (Distribution, HTX-6, HTX-2, LL Power) or continue to mount as installed from the factory?

All the communication on the forum has me sold on investing in this package - I love that LL is involved in the discussion.
We are very excited to extend our boating afternoons/evenings with some underwater light - the boating season is never long enough.
In one post I found elevatedconcept shared a photo of a tidy installation placing the Power Supply Box together with the amps.
Can I plan my distribution block layout to accommodate the 8ga required for LL, using a singe 1/0 from the battery? Or must I chase the power directly back to the battery (switch)? (I fear it would be >10')
Again, I believe the TT2 can control the underwater lights. Do I need to chase a switched wire somewhere? Is there already one that I can relocate?

Thank you in advance for the help. As I work through the project I will try to update the post on my end as reference for future users.