a modern ‘trail’ hardtail, with large-ish tyres (2.2″ to 2.4″) at sensible pressures (low-ish) should see you right.
or, if you’re full-suspension curious:
specialized camber
giant trance
Other great bikes are available, but you should be able to find a shop near you selling one/both of those for you to try/buy.
(they may well have other great bikes, they’ll tell you all about them)
shimano ‘deore’ is great, even if it’s not as expensive as slx/xt.
as a rough rule, shorter stems mean less scary descending, longer stems help keep the front wheel under control on loose climbs. There’s a compromise, try different stems.
(there are dozens of ways to adjust the way a bike feels, stem-length is a simple, and effective way to make a big difference)