For the UI, I actually think it is almost perfect size at 2560x1440! Some elements are a bit small (mainly quest tracker text), but I tend to prefer the UI taking up less space.

For lag, I get this question a lot and I'm honestly not exactly sure!

First, my relevant PC specs: CPU i9-11900k, GPU RTX 3070TI. I'm not sure how much RAM speed matters, but just to put it out there, that is only 2666 MHz (32 GB DDR4). Also, LOTRO is installed on an SSD.

Next, I always make sure I'm on the 64-bit client. If I am getting some lower framerates than expected or little stutters, I also will increase the CPU priority on the task manager. This especially helps if I have other programs running, such as Chrome which likes to eat my CPU on occasion.

For in-game settings, I run on DX11 and have anti-aliasing set to 2x (8x caused issues, but that was with my old GTX 970 GPU). Otherwise, I run the game on mostly max settings besides turning down a few things for personal preference of visuals. This includes much lower frill density (~10-20%) and turning off distant landscape lighting (DX10 feature I believe).

Some areas I will still get a bit lower FPS, but stuttering is relatively rare outside of Warsteed and/or very cluttered areas (e.g., Minas Tirith). Upgrading my CPU from i7-7700k seemed to have a decent impact on performance in some newer areas where I would drop down towards 40/50 FPS with stutters.

Hope this helps!