Best Hardtail Under £1000 vs FAT Bike

Hi Guys - I am new - Hello. Would appreciate some advice please?
I currently own a Trek Farley 9, which is an absolute beast - predominantly used in Pinewood trails/Beach.
I want to get myself a 2nd bike, thinking a MTB, so I can see what my routes and new routes would be like with smaller tyres than the FAT bike.
After some research I have decided on to go with one of the following (Voodoo Bizango Carbon/Vitus Sentier 29/Boardman MTR 8.9 or Calibre Bossnut)
Which one would you be inclined to go with?

Also would anyone recommend upgrading the Forks from Rockshox Bluto to either a Charger 3 or a Manitou Mastodon Pro STD 120? which I hear are next level?
Lastly - does anyone know if you can run tubeless with Schwalbe Jumbo Jim Tyres 26x4" on one of the above MTB in case I love the bike and want to switch it to Fatty tyres?
Thank you
Chris