Dokebi

What kind of amp? I usually prefer film type (polypropylene) capacitors to electrolytics for coupling signals. I would also parallel film and electrolytic together for the best signal frequencies to come through. You really can't go wrong with any of those choices for power caps. No such thing as overkill in audio so use the most expensive blackgates. The only conflict might be that blackgates are abnormally large for its voltage and capacitance so you may end up requiring quite a few compared to elna's for power.

I think smaller snug holes are better than large because you will need to fill the gap on larger holes with excessive solder.

For the cmoy amp you can use any pot between 10k-100k. Just change R2 to accomodate your pot. Lets say the original article dictates R2 is 100K OHM when using a 10K pot. If you wanted to use a 50K pot you would change R2 to 500K, 100K pot R2 would be 1MEG. Good luck!

Nice work