The JJjr sounds great at low volumes, crancking is 11 o'clock max IMHO, after that it starts to get overly compressed.
The JJjr has a great FX loop, so you can use your FM3 for effects, they will be better than the TAE.
Whisper volumes will not work unless you use the headphone output on the TAE. Simply the 2x12 needs some volume to sound decently. The Class-D amp in the TAE is cool, but still you will need to push the 2x12.
The cab simulation options are limited compared to the OX or the Captor X, but you can load IRs, 1 at a time.
The Boss TAE software is 1990 compared to the Ox or the Captor X.
If you don't plan to gig, get an OX, it sounds great and the effects are very good, but effects are only for the line out, not for the cab out. The app is really cool, you do not have full flexibility on the mics and rooms, but sounds great. The room mikes are the sheet on it, it really sounds like an amp in the room in headphones. (minus the air moving and pants shaking)
The individual mikes have Eq, plus you have global EQ, compressor, delay, plate reverb.
The attenuator part is garbage below 3.
If you are gigging the new Captor X is really cool, great speaker simulations, almost full flexibility on the speaker sims, distance, axis, front, back ton of mikes. You can load 2 IRs at 1 time and you can blend them. Has a "Twin Tracker" artificial double tracker feature and stereo reverb or ambiance, EQ, enhancer. Has a 3 level attenuation, no effects on the real cab. Roughly half the price of the TAE and the OX.
The TAE is cool, the variable reactive load is giving you some tone shaping options, effects are sent to the cab too. Has an effects loop, compressor, delay, reverb, separate EQ for the Cab out and the line out, can switch channels of the JJjr.
If I would buy something knowing the FM3 is coming, I would choose the Captor X. Just my 2 cents.
(And yes I have all 3 of them and a JJjr, and not forming an opinion based on youtube videos.

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