So... there's several issues with the souls bar, I can split these into separate issues if needed but wanted to address them all here to reduce issue spam:

• The soul bar shows decimal points. This can be very confusing to deal with especially with the Corrupted Beacon which will leave you with an odd amount of souls left, and having "half a soul" makes little sense!
• The position of the soul bar overlaps with the off-hand item slot causing a visual conflict between the two elements
• The font for the number of held souls lacks a black border like the level number
• The soul bar is displayed in Creative mode even though souls aren't used. It should probably be hidden like the experience bar
• Stretching is occurring (at least on a wide-screen monitor), resulting in the left side of the bar touching the edge of the screen with a normal display and the right side of the bar stretching its pixels to connect to the inventory:
  
• I know it's hard to find a good place for something like this, but given its ties to the artifacts, what if the souls bar was displayed above the artifact slots? Its visibility could then be tied to the artifacts bar so hiding/disabling artifacts also hides the souls bar. Here's an example of what I mean in a quick mockup:
  
  Whether or not it should have numbers and/or a soul icon to make it clearer could be worth discussing.

Regarding showing numbers on the soul bar; I don't believe the number is really necessary - in Minecraft dungeons you don't normally see the exact number of souls you have unless you hover your cursor over the bar, since by design it's more of a "power bar filling up" type thing, kinda like the amount of experience you have (not the level number).

We're woprking on a wiki page to make it clear how you as a user can move the soulbar around. I hadn't considered incorporating the stretching into it and that's a valid point.

The number is there to have parity with the Experience bar. I do agree about the decimals being weird, as well as it showing in creative mode. We'll make those updates too :)

I used to have a black border on the font, but then we received remarks that our gui elements were causing a "significant" drop in FPS. After analyzing, the black boarder was part of the problem.

Glad to hear there's ways to position it better, though I do hope my suggestion can be considered as a default since it looks a lot less like a placeholder that way!
That's fair on showing the number, if an option exists to hide it that'd be great too - for that pure Minecraft Dungeons experience and all.

The FPS drop sounds strange, assuming the vanilla HUD doesn't lag much I wonder if it's something to do with Forge?

Thanks for the positive feedback, it's a breath of fresh air and I look forward to seeing how the mod progresses!

Just a slight correction to my previous statement: number of held souls isn't shown at all in Minecraft Dungeons.

EDIT: Also, if the soul bar were to be given a unique visual it would be distinct enough from the experience bar to not need a number shown.