So, yes, these technically should be submitted to the respective currently existing threads, but they appear locked and I have no other way to add these, so I'm making a new thread here.

In general, I have very few issues with the Encounter Builder tool, it's super helpful and very well done like most of DnDBeyond's assets.THe only recurring bug I've seen is some creatures listing spot remaining the same regardless of what filter(specifically CR as that's what I shuffle by most often) I use when searching for monstsers. However, as a DM with several NPC characters built that are designed and intended to be adversarial to my players, having the option to create encounters using Character List characters as NPC/monsters would be fantastic, though I can understand that that may be technically difficult to implement.

My larger - but still relatively small - issues are with the Combat Tracker tool. I understand it's in Alpha still, so lots of bugs and features to work out yet. But when the Survey link brings me not to a survey page but a survey-building website login screen, I cant really use that to input my questions and concerns now can I. However, my issue is probably one that has already been brought to the attention of the Dev team, who are famously receptive to feedback. Live Player HP tracking. Linking the instanced character in Combat Tracker to the controlling player's Character Sheet in real time - or on a delay as might be easier from a technical standpoint - would remove a lot of second-guessing and frustration for both player and DM. Especially when dealing with players who are fresh to DnD and don't necessarily understand how everything works. It would also cut down on time spent clarifying what needs to be done after combat(long rest vs short rest, potion usage, spell necessity, etc) and since tracking HP is one of the more tedious aspects, to me anyway, about combat in general, it would be nice to not have to worry about it.

I appreciate the time the Dev Team has taken to add these features as QoL assets in what is already the best DnD online tool available, especially since they were released during the most frustrating development time in recent history.

The encounter builder is still in beta, so it is still far from an actual "release" or a final product. As a GM, I strongly recommend using the monster homebrew tools to create proper NPC statblocks rather than using the player-oriented character builder. The character builder has a better UI so it is easier to use, but it is extremely limited in the stuff you can create (unless you want to homebrew a ton of subclasses/feats/items). The monster homebrew tools has a pretty ugly UI and it is not super intuitive, but once you become a bit more familiar with it, you can do a lot more with that tool without using other homebrew tools. And as you have noticed, it is a lot easier to integrate NPC statblocks on the enemy side using the encounter builder. Statblocks are also much easier to navigate and run, and if you have older or weaker hardware, running half a dozen statblocks is much easier on your device than half a dozen character sheets.

I think they will eventually get to letting people put PCs and NPCs on either side to reflect NPC allies and PvP situations, but that seems pretty far down the bucket list so I would not hold my breath over it.