Hi, maybe some ideas to simplify your buying
Here is rob buying list: prices are mentioned in GBP
ROB:
1 rear shock superdeluxe ultimate 210x55-293
2 shimano m4100 casette-35
3 shimano mech m5120 40
4 shimano hg54 chain -14
5 shimano rt rotors 36
6 shimano m4100 shifter
7 brakes m6120 4piston 149
8 one up v2 dropper -222
9 magic mary/big betty tyres
10 wtb volt saddle
11 nukeproof am bars/stem - 66 45x35x1.1/8" - but on video I see raceface (turbine 35?)
12 nukeproof neuron v2 800mm 800x25x35mm
13 bushings -> extra order
14 ergon grips 21
15 chainring tool 14
16. wheels DT SWISS H1700 mullet (probably with 35mm, 29front, 27.5rear)
17. rockshock fork zeb ultimate, 44ofset, 170mm travel
My buying list is quite different, based on parts availability and probably quite different setup. Maybe wrong mabe right, time will tell

. I order from bike24.de, hibike.de. ALso bike-discount.de is OK, but during my buying no extra prices. I also found that a lot of parts are quite cheaper on local market, so maybe Italy as strong cyclo country is same. Bike24.de delivery is 3-4 days (if in stock), bike-discount longer (said on item +1-2 week shipping, depend country 2 country).
Note, that due current covid situation the stocks are empty and ususal winter sale is not happening. Maybe something, f.e. bike24.de has a sale tommorow. But you need to access page daily.
Mgx:
1. rear shock rockshock ultimate 210x55 -> i bought rockshock ultimate 210x50 opened and refited to 210x55. 210x50 was on stock and cheaper, 210x55 delivery was 3 month (WTF?). I think also 216xXX will work with offset bushing, but i wait till somebody confirm/deny

. 216x55(60) can be more available . Also there is way to use coil version ( i dont found any vivid on stock). Or cheaper shock (not from ultimate but select plus)-> ebay/discounts from 150e. OK when you dont run downhills for long

2-4 drivertrain - i found discount on XT family 2021 (12 speed) for 200eur, so i selected instead SLX (SLX was for 159, not available in slovakia due supply issues). I think that 10s can be better for motorized bike, but lets try and see...
- casette Shimano Deore XT CS-M8100 12sp 10-51 with microspline (new standard)
- chain Shimano Deore XT M8100 12sp 126 pcs
- rear derailer Shimano Deore XT RD-M8100 SGS 12sp -extra long
5. Shimano RT 66 6nuts, 203 front, 180mm rear - make sure you order proper (6 nuts version or whatever you use). I will change to 203 rear probably with adapter later
6 . shifter XT SL-M8100 1x12sp right ( I-Spec EV )
7. brakes m7120 4piston (SLX), I-Spec EV - cheaper, XT benefit is only 9 grams as far as i remember.XT was 100E plus!
8. same one up v2 dropper + i ordered Shimano-I-Spec EV mount - make sure the correct size- i think 150 for S size - better to check. For M i ordered 180mm and i will downsize to match frame.
9. magic mary 2.8. Maybe too match, later 2.6 maybe!
10. volt was gone, so i bought pure. I try to look for old laser V - but gone!
WTB Pure ProGel Sattel. I bought basic WTB pure (no progel!)
11. i selected cheaper 31.8mm Truvativ Hussefelt
12. bars 31.8mm/720mm (trails in HT are narrow). This 31.8mm is OK for bafang display also. later i can upgrade to 35mm bars if needed
13. same bushings -> extra order (bafang, you need to know rear shock and geometry when ordering. From order 2 home 1 week.
14. fsi grips - extra chunky
15. same as rob-> ebay/local BB29
16. 27.5+27.5 DT SWISS H1700/35mm with microspline option
17. zeb ultimate 27.5x 44offset 190mm (i can reduce travel if needed). fork was -100e cheaper.
alternative - if you are friend of lower travels -f.e. this can be HOT SALE for you
RockShox Lyrik Select Charger RC Debon Air 27.5 Inch Fork - 160mm - 46mm Offset - Tapered - Maxle Stealth - 15x110mm Boost - Special Offer
18. pedals-> rob does not mentioned -> i ordered One up composite blue.
I think 170mm is just right for 27.5 and also for mullet setup (29.0 front). I am not aware that size of bike make here big change, but i am not a setup expert, its just my feel.
Happy hunting