Wow, that looks incredibly detailed, definitely very useful. As for feedback and suggestions:
1. The first map looks a bit blurry, I prefer the second one, more details are noticeable.
2. The Legends section looks pretty good.
3. Try color coding each area uniquely. If the background is dark, the colors need to be bright to make it easier to read and the text/legends need to be dark to contrast with the zone's color. If you use a light background, the zone colors should be dark and the text/legend should be in light colors. Its a Power Point trick that helps visibility immensely. And with unique background colors and with a legend for those, you can find the zone you are looking for at a glance.
4. The map looks really visually busy, this can be solved with an added table after the map. Separate items by category (weapons, consumables, sanctuary offerings, etc) and each category gets a unique color. List each item in the category alphabetically and give them a unique ID (consumables might occupy ids 1-10, which mean weapon IDs would start at 11). Use brackets to express quantity, for example, 15 can indicate a Kureimoa and 23[10] means 10 Waters of Blessing. Use < and > to indicate a Mimku, such as <147> indicating the Aristocrat's Set guarded by the Mimku. Now players can see the info much more easily.
5. Please make some legends for NPCs as well and quest stages, such as "Thief (stage 3)" using the previously mentioned system.
6- Use a paired colored key and lock to indicate switched and what they unlock, as well as keys and doors.
7- You could use a dotted out door to indicate secret passages ( for example: http://game-icons.net/icons/delapouite/originals/svg/secret-door.svg)
8- Use the Redshift icon to indicate that type of barrier.
Hope that helps. This could easily become the single most useful resource for a Salt player, can't wait to see the next iteration :)
The twinmetal ring doesn't exist, it was confirmed by one of the devs in LobosJr's stream (see the chat): https://www.twitch.tv/lobosjr/v/55958633?t=299m20s (I linked the timestamp of the question, her answer is about two minutes later).
AFAIK classes only change your starting skill points, as you progress through the game, you may be changing your profession.
Here's the builder to get you started what the different classes skill points are set to and to play your build through the game.
Not sure if the bonus has any negative effect, I chose no bonus when I started but in case you plan on playing co-op, be sure to get the Sellsword as bonus item.
I started out as thief and currently I'm a Swordsman/Cleric with Swords rank 4 and Cleric rank 3 to further point out that you may change your build along the way.
Shelldragon (one of the devs) just confirmed on Lobosjr's stream that it didn't make it into the final game.
Here's a link to the VOD, the question is at 4:59:20 and the answer is at 5:01:20 (all in the chat).
I've done a bunch of playthroughs on all systems, and yeah PC is the only one with any noticeable difference in terms of performance. Personally my go-to is Switch, just more comfortable for me. Plus if you grab an 8bitdo Pro 2 you can actually play with dpad instead of analog stick on Switch, if that's something you're interested in.
https://www.amazon.com/dp/B08XY8H9D5/ref=cm_sw_r_cp_awdb_imm_TT9E0E2N8G88VW8B5FVC