The second playtest

The second playtest included all playable content of the game: the level as a whole, character progression, enemies, treasures, functioning shortcuts, and two bosses. 

The test itself went much smoother than the first. It was conducted on the same PC as the first so I could see if the performance had improved. The game's default graphic scalability is now set to epic instead of cinematic and I assume that my custom-made materials are more lightweight than the prototyping materials I used earlier. The graphics card's VRAM ran short once again, but only by around 100 megabytes. The frame rate doubled compared to the first test's and the input lag was gone. 

The playthrough of the level went smoothly without any issues or difficulties. Both of the bosses took several attempts, which was within my expectations.

I was initially worried that one of the first boss' abilities was unclear. The boss jumps and slams the ground causing an earthquake that damages the player if they're in touch with the ground (first seen in the playthrough vid at 7:31). I was pleasantly surprised that after getting hit by it my playtester said: "Oh, so you got to jump, huh?" And that's how you avoid it.

The second boss had an issue where it would execute multiple attacks at one go when its health got pushed past certain points during a single special attack execution. This was due couple of issues between the old boss code and the new AI behavior tree. While doing fixes for the issue, I figured couple of ways to make future behavior trees more responsible for all of the boss' actions which should result in more simple and readable code.

Below is a video of a full playthrough of the game after fixing the issue mentioned above.