Hi there,
Re rim tape, I've never run tuffs with tape, just inner tube and tyre, and no problems.
Re axle nuts, they're 3/8ths diameter, but in my experience the pitch (or tpi - threads per inch, as they're imperial) seemed to have been randomly selected by Skyway BITD. I've had both common sizes with Skyways over the years, both 24TPI and 26TPI.
But please, this is just my personal experience others on here may have far better knowledge/experience regards this matter.
Unless others can provide better knowledge the only real way to be sure would be either:
1. measure an inch of the axle threaded area and count the number of threads (bit of a ball ache)
2. Buy a Thread Gauge like one of these
https://www.ebay.co.uk/itm/2-piece-thread-pitch-gauge-set-metric-and-imperial-SAE-Laser-7691/333504102222?hash=item4da664bf4e:g:Vu8AAOSwzQFeLqXL and measure it.
HTH's