Let me answer the easy question first, power supplies don't neccesarily have to match. You could run a Hicap on the gain stage and a TPX1.5 on the TA section or the other way around or any other similar PSU.
I used a teddycap on the digital side because I had one - the exact type is even less critical on there.
Due to the way I'm powering the various analogue stages, directly from the Hicaps, I had to provide 24v for the output relay and that came from the Teddycap also powering the digital side. Hence needing a 24v supply instead of the napsc.
The earthing mods are a bit more involved - I changed the reference point for the potentiometers and the gain stage feedback capacitors to the main star earth.
Theoretically, this should be better because of power currents flowing from the main star earth to the sub-stars by the gain stages. Whether this actually makes a difference, I don't know as I did all the mods at once.
As well at the TA mods mentioned above, I also doubled the size of the tantalum input and output capacitors. Electrolytic caps create distortion dependant on the AC voltage across them. Increase the size of the cap and the distortion they add to the signal decreases.
Same is true for Polyester caps but the effect only shows up at larger AC voltages. I haven't seen anyone test whether the same is true for tantalum caps but I thought I'd experiment.
If I was starting again, I'd probably leave the earthing mods out and modify the HiCap for the gain stage into two separate 24v supplies with separate earths each going to the respective sub-stars by the gain stages.
This would remove the psu currents from the link between the sub-stars and the main star. The pots are currently referenced to the sub stars. I would add a direct link from the feedback capacitor to its respective sub star.
If this all sounds a bit too much, there are a set of other mods for the 102 that were written up into a pdf by a fellow PFM member that are quite easy to follow. I can't find the exact link to it at the moment but I'll have a further look.
EDIT: PDF was by Neil James - possible link to it here:
https://pinkfishmedia.net/forum/threads/naim-102.154646/