So I did the last stronghold (enjoyed it and was much better than the horrid second one).
Am on WT1
Observations so far.
Feels like first 10 levels of game where equipment is higher score but no better or worse than existing equipment.
So hardly any enemies drop equipment, if there is a drop its a mod 9/10.
Main source been normal vendors (expensive) and chests. As has been stated it seems WT1 onwards clan vendor sucks.
It seems I can either equip higher score equipment or better equipment as my equipment from level 30 is higher armour and attributes than score 285 equipment.
How does the loot scoring work, am I ok to junk the crappy equipment I keep getting and will I still be able to get higher score equipment?
Can I e.g. temporary equip the high score equipment so I unlock the strongholds, but then unequip it after mission started and put my better stuff back on?
I did a control point and not even the 2 elites dropped any equipment.
Does the equipment get better or is level 30 the best?
As you progress through world tiers the gearscore brackets change and correspond with an iLevel which has a min and max roll for the range you are in. EG: WT4 is iLevel 34 and has a range of 400-450 gearscore for drops. wt5 will be iLevel 35 and a gearscore range for drops of 450-500. Any additional health of armor you get to your base stats as you progress through the world tiers is related to iLevel - not gearscore.
Gearscore deltas in terms of your gear vs content is irrelevant if you are still within the range of the world tier so your question of putting on gear to unlock the stronghold entry then putting on gear that makes sense is correct - that is possible to do.
Gearscore seems to be in place to gate players at the moment as you don't get a bonus for being overlevelled when still within the range of that tier - it is simply related to the iLevel of that gear. Also why I am personally not bothered to push further than 450 in wt4 at the moment - it will still be an iLevel lower so my max range of potential stats will be too low in wt5 regardless of gear score.
Wt5 from what i can see is the exact same however post wt5 ie: raids potentially where they will introduce a gearscore climb for worlds first events etc will incorporate a formula that checks your overall gearscore as a multiplicative of an "end game power" which is a flat value currently in the files. So this will still keep wt5 thresholds for most content, but will have the ability to flick a switch and actually relate content to your gearscore as they push more difficult content.
I put in bold the answer to your question as I sorta went off on a bit of tangent to explain it properly