building up a fargo with 100 front and 148 rear, although I think I can get reduction plates for the rear for 142 (never seen this in practice)

I just picked up a 2017 fargo frame. I need to build it up and I'd like to be able to switch it easily from on-road/gravel use to more legit off-road bikepacking. My thought was to get two separate wheel sets, a 29 set for road/gravel and a 27.5+ for more off-road. Especially with tubless set-up, I don't really want to mess with swapping tires all the time.

The alternator dropouts are 148mm but can accept 142 with a "reduction plate" I've never seen the reduction plates, so I'm wondering how easy they are to swap in and out. Should I really try to have both rear wheels 148, or is it easy enough to put on the reduction plate and have the 27.5+ be 148 and the 29 be 142? My gut feeling is that I'd like them both to be the same.

Side note, recommendations on wheels? It seems that buying pairs it is more difficult to get a 100x15 front (fargo front fork) paired with a 148x12 (most 100 fronts seem to be paired with a 142).

I can see DT Swiss conversions to change out this rear axle to a 142 x 12, but does anyone know if this can be converted to a 148 x 12?

So I have a moots ybb superlight that I've had for 20+ years. 26" wheels, v-brakes, 3x9. Great bike in it's day. I've done a couple of road tours and one bikepacking trip on it. I've run it with flat bars and with drop bars. The stopping power when loaded is not so great. Is this bike worth upgrading for bikepacking use?

I can drop some money and upgrade it. Maybe a front disc brake. Could definitely use tubeless wheels. Could always run a new 1x11/12. I am wondering if tires are going to become more and more scarce for 26". And the front shock is pretty old too...how much longer am I going to be able to keep that maintained (not sure I can anymore). Could always go rigid, Salsa has an ok looking 26" rigid.

On the other hand, by the time I drop any significant $$, it might be worth looking at something new.

Thoughts?