Tall and heavy new rider

At your weight, If you really intend to do MTBing, get the best bike you can afford. Air sus is a good idea. You’d struggle to find a coil shock that’d be able to cope. The Fathom has thru-axles, which is a Good Thing.
If your gf is a dedicated rider, you’ll struggle to find a do-it-all bike that’ll let you keep up with her. In this case the F2 is not a good choice since it has an 1X drivetrain.
It/you’ll spin out at below 25 mph.
Changing a cassette won’t help. They (generally) don’t go below 11T. Your limitation is the chainring/crankset.
If it was me, I wouldn’t appreciate the 120 mm fork and the slack headtube angle for road riding or even fast XC.
You could get another wheelset. See if there are compatible hubs in 36H. Build new trail wheels around these. Use the stock wheels as your road wheels. Maybe trade in a 34-36T ring to keep up with the gf better.

I did see shimano makes 2 crank sets which might work. Not sure about fitment though.
https://bike.shimano.com/en-EU/product/component/slx-m670/FC-M677.html
https://bike.shimano.com/en-EU/product/component/slx-m7000/FC-M7000-10-3.html

Really between the two bikes the only real difference is the better derailleurs and brakes on the 1. So which one to buy? If you don't plan on riding much I would go with the 2. I'm not so sure about this spinning out thing that one of the posters mentioned because the smallest gear on the cassette for both is a 11 while the front chainring on both are a 30, that's the same gearing; where the 1 is a bit better than the 2 is the large gear on the cassette is a 46 vs a 42 on the 2, which the 46 would be great for difficult uphill terrain, but if where the both of you go cycling has no challenging steep off road climbs then I would get the 2 and save a bit of money. Even if you get the 2 and later you say, gee I need a really low gear to climb a steep grade, ok you can to the LBS and they can sell you one with the same gears as the 1 has! But how much is that cassette inquiring minds want to know? Around $75 plus labor if you don't know how to change the cassette out yourself, so you would save about $200 on the 2 over the 1 after a new gear purchase.

Personally I would go with the 2 because there isn't any real discernible difference between Deore and SLX other than money. If you do decide to swap the gears out keep the old gears if they're not worn out when you make the swap, you never know when you might need another cassette especially MTBing..

greatscott said:

Really between the two bikes ....

The OP mentions THREE bikes,Talon 2, Fathom 1 and Fathom 2.

greatscott said:

I'm not so sure about this spinning out thing that one of the posters mentioned ...

The OP says he also wants to do some road riding with his GF and want a bike that can keep up with her on her ROAD bike. That could easily become difficult with a 30/11 top ratio.
Not much of an issue while MTBing though.

greatscott said:

...the smallest gear on the cassette for both is a 11 while the front chainring on both are a 30, that's the same gearing...

The T2 has a 36/22 crank. 36/11 would help with keeping up with the GF.
But sure, the F1 and F2 has the same gearing.

greatscott said:

Personally I would go with the 2 because there isn't any real discernible difference between Deore and SLX other than money.

Generally I’d agree.
But I believe the SLX derailer has the clutch feature, which is an advantage WRT controlling chain slap when using the big cassettes.

Orkid1989 said:

I did see shimano makes 2 crank sets which might work. Not sure about fitment though.
https://bike.shimano.com/en-EU/product/component/slx-m670/FC-M677.html
https://bike.shimano.com/en-EU/product/component/slx-m7000/FC-M7000-10-3.html

Can’t really help you there.
Bottom brackets have always been kinda messy. Different threads, different spindle lengths, different bb shell widths. And ”now” the bike industry has tossed a handful of press-fit standards into the mix as well.

dabac said:

The OP mentions THREE bikes,Talon 2, Fathom 1 and Fathom 2.

The OP says he also wants to do some road riding with his GF and want a bike that can keep up with her on her ROAD bike. That could easily become difficult with a 30/11 top ratio.
Not much of an issue while MTBing though.

The T2 has a 36/22 crank. 36/11 would help with keeping up with the GF.
But sure, the F1 and F2 has the same gearing.

Generally I’d agree.
But I believe the SLX derailer has the clutch feature, which is an advantage WRT controlling chain slap when using the big cassettes.

All my comments were on the Fathom 1 and 2, not the Talon 2, I left that one out because it's too low of quality compared to the other two in my opinion.

There are other options, one bike got rave reviews on Amazon as well as on some other sites, made by Beiou

That Beiou is a little off the mainline of bikes but it's worth considering, but if you need to ride it first before buying I would look at the Specialized Fuze Comp 27.5 but again it won't have road speed gears; a lot of mountain bikes are getting away from the double and triple chain rings. Other worthy contenders, but again single chain ring, is the Kona Cinder Cone, Trek Roscoe 8, Diamondback Overdrive Carbon Comp, and Orbea Laufey 27+ H30; the last one by Cannondale is the Cujo 2, this bike is on par with the others I mentioned however Dorel Industries that bought out Cannondale is at the verge of financial collapse with a 77% chance of going bankrupt in 2 years, so this could mean you might be able to find a really good deal on a Cannondale but after the bankruptcy there wouldn't be a warranty on the frame, but most frame warranties aren't worth the paper their written on anyways.

It looks like with all the mtb bikes going to a single chainring the op may have to look at hybrid bikes if he wants to do both trail and fast road riding.

I think fathom 1 and fathom 2 is best.