I thought waiting until level 45 before entering certain cells, dungeons, etc. As well as beginning quests would guarantee the strongest, most powerful leveled quest rewards/artifacts. However, a long time ago, someone told me that one would actually have to wait until level 65 or higher to accomplish this. Any truth to this?

It can vary from item to item I think, but I'm sure you can check on UESP for the max level

EDIT:I just checked and I the highest I found out of all the items were level 46

I'd rather not look up every item. I would much rather just get myself to the required level to guarantee everything will be at max.

Wow, you were able to check that fast?? Does this include max level of followers as well, and all items from DLC?

Yes, followers can be checked too, but I don't think there are any leveled items from the DLCs

Interesting...

The highest I've seen for items is level 46. I usually wait to do certain quests until I reach that point. I probably shouldn't since I rarely use unique items, but I do.

Examples include (spoilered to hide spoilers):

Where did I get the idea that it was level 65, I wonder?

my level 54 char already found heavily valuable enchanted Ebony and Glass items.

Level 46+ for skyrim.

No leveled items in Dawnguard as far as I could find.

Level 60+ for Dragonborn.

NPC's (including followers) level up with you up to their max level, so don't worry about finding them too early.

There is an exception to that, I believe. One follower is locked in the moment you enter his/her cell I read, and will not level up with you unless you use console commands. I just forget which.

Hi! This is a bit OT but is J'zargo the most powerful companion in the game? Is he the only one without any level cap?

For vanilla skyrim, yes he is. All the houscarls top at lvl50, and the other members of the companions top at lv50. Next lowest is 40, and then 30, and lots of 20s. It appears followers stop being useful a bit too soon.

I didn't check for Dawnguard or Dragonborn followers.