I played around with a C64C (250466 board, VIC-II Kawari Mini, Pi1541, Kung Fu Flash 2, a 1571 drive, Keelog PSU and a CRT TV).

The Kung Fu Flash 2 had a cold solder joint on the SD card slot, but that was easily fixed.

The 1571's internal Mitsumi PSU was apparently in-spec (5v and 12v rails were with 5%, less than 30mv of ripple assuming I can trust my scope and my methodology) even without load. I forgot to check whether the drive mech is a D502, which purportedly has the same head death issue as the D500 (looks like it from the front), but at least the single side used in 1541 mode works. The 1571 was in storage in one of my closet for about 29 years until I tried it again. Fun fact : it was either sold or serviced at Datashack ( VG Datashack ), based on the stickers on it. Not surprising, as their old location is a walk away from where I live.

I also have a 1541 with I think is an Alps mech, but that is still untested. The 1541 had been sitting in its original packaging for a probably for 10 to 20 years or so on a shelf (seem to recall seeing it many times over the years ) at a local flea market stand when I eventually bought it.

I have another pi1541 hat on order that supports option b (IEC bus daisy chaining). I accidentally bought the wrong one.

The Kung Fu Flash II's REU emulation works fine with Sonic.

The VIC-II Kawari Mini works great in NTSC mode and NTSC 50Hz mode on my 13-inch Disney princess CRT TV. I need to look into seeing if I can Y/C , YPbPr or RGB mod it (it has an integrated DVD player that shows no dot crawl or other composite artifacts, so I expect to be able to tap into that).

My time is very limited these days, so that is likely all for a while.

EDIT: Sorry if I am doing something "sacrilegious" in the opinion of C64 fans. This is my first C64 ever. I low key wanted one since I first experienced one, on a black and white TV, at friend's place, in the mid 1980s. Only ever toyed with emulators since, until I bit the bullet at VCF Montreal this year.