Awarding XP

[orobouros]

Instead of using the Gold = XP option, I've started giving the party 100 xp for exploring a new hex, and 50 xp per room in a dungeon, on top of the monster XP.

Not bad. This gives a nice low-level bonus while not affecting higher level groups much, since the award does not scale to the character level.

For longer term play, does it make sense to switch over to gold=xp, or after a couple of levels are characters survivable enough to go after the monsters directly?

XP for gold is a good way to incentive exploration and creativity instead of just plowing through a dungeon room by room. The treasure chest surrounded by giant spikes and tons of broken, smashed bones of humans, orcs, and even a few Minotaurs will hopefully make it clear the players either have to come back later (with better spells and more HP) or come up with a REALLY smart way of avoiding the traps.

Likewise, even first level players are capable of handling powerful monsters. However, they have to be prepared, have several contingency plans, and a bit of luck. But if you can spike the guards' ale with a sleeping potion, it doesn't matter much that they're level 5 thieves and you just started adventuring.

[Seven]

Part of the problem is that characters level at different speed.
In theory the XP for gold is awarded when the gold is brought back to the base, deposited in the bank or whatever is appropriate. That's often dictated by how much the party can carry, if that is tracked.

I don't see any problem with a Thief character leveling as soon as the XP is earned.
The low success rates for thief abilities certainly hint at learning through trials and errors. A Cleric, on the other end, could need to go through some rituals, especially to learn new spells. The Magic-User absolutely needs some coaching to access those new spells.They shouldn't just appear in his book. The Fighter probably just needs to hang around a higher level fighter for a bit. Any village will probably have a Fighter and a Cleric who can provide training. Possibly a Magic-User as well. A Thief instructor could be harder to find, if one was required.

I definitively would not keep a thief from leveling as it's one of the few perks he has.

[Hackworthy]

Initially I allowed my PCs to level when they rest but it tended to bog the game down because of the 3 spell-casters looking up spells while the 2 the non-casters twiddled their thumbs. Now I just do end of session, as is recommended.

[Dimirag]

You can combine both, level them up while resting, but let spell research and learning for the downtime, they will get new spell slots to use with their copied spells but will need to copy new ones or research them in a lab or other place.