I would work out in your mind, honestly, what sort of trails your likely to ride. As IMO a 100mm hardtail is just right for 99% of Glentress e.c.t but that’s not to say more travel is wrong!
An anthem would easily double as a race bike, maybe make the hardtail redundant…if you like the anthem, I hated mine! But putting my dislike a side not sure the Anthem will be that different to your Hardtail, will have more comfort (and a bit more control due to the rear not bouncing around as much) but you will still have racy angles which, although not a problem, will not be as confidence inspiring.
If your looking to buy an extra bike I would look more at the trance style bike, 120mm + with a more relaxed head angle. If your looking for more do it all to replace the hardtail either, look at the something like the anthem or maybe better with slightly less aggressive head angle a trek fuel or scott spark.
Or could look at a 29er as an all rounder ,if you want more confidence on downhills.
Or if you like your current bike, try playing about with the set up, try a shorter stem/wider bar, a bigger tyre up front even an adjustable fork or longer fork (with in reason). Dropped post maybe.
As I said at the start, IMO I find a 100mm hardtail just fine for Glentress and if it’s mainly that you want to feel more confident on these sort of trails then practice is the best thing, a boring answer I know, but I used to struggle on downhills but (after A LOT of years riding and racing) DH sections are my strong point. So maybe just need to persevere and tweak your current bike. But if it’s that you really want to ride more advanced trails, often, I would look at something slacker, head angle wise, rather than extra travel, usually extra travel comes with this but not sure replacing/adding to your current ride with an anthem is going to help much.
And yes I agree road bikes are easier to understand!