The reinforced fist and ReWired plasteel fist can mine blocks of a very high mining level.
Meteorite block (mining level cobalt), diamond ore (mining level iron) and orichalcum ore (mining level duranite) can all be mined with both fists.

Obsidian however can't be mined even though it is mining level diamond. Tiers below cobalt or duranite.

I have not altered the config that would change the mining level of either fist

Check the harvestable mark in the top left of the screenshots

There's probably a conflicting mod here, try reducing the mod list, starting with that pokemon one

Metallurgy 4

TAIGA and Tinkers

Just cyberware and REwired

It seems to not be a conflict. As can be seen in the last screenshot the diamond ore can still be mined even though the mining level of the reinforced fist is supossed to be stone.
The mods installed are Jei, hwyla, waila harvestability and of course cybereware. I have also tested without REwired but that wasn't the issue.

The reinforced fist seems to be able to mine anything except for obsidian.

The configuration defines the mining tool equivalence:
1 = Stone pickaxe
2 = Iron pickaxe (default)
3 = Diamond pickaxe

What makes you think the mining level is supposed to be stone?
What value do you have for "Configure the mining level for the reinforced fist" in your configuration file?

The tooltip implies the mining level to be that of a stone pickaxe.
I would image that means:
1= Wooden pickaxe
2= Stone pickaxe
3= Iron pickaxe

I haven't changed the config at all in the recent tests. It is indeed set to 2.
If you are right about the values that would mean that the tooltip is not accurate.

Regardless I'm still able to mine anything above diamond level which definetely doesn't add up.

Try mining those ores with an iron pickaxe?

The 1/2/3 values are fairly obscure in the configuration file anyway. I would expect the equivalent tool registry name to be there instead of those magic and undocumented values.

The iron pickaxe cannot mine any of the ores (except for diamond). The stone pickaxe cannot mine diamond or any of the shown modded ores. This seems to be exclusive to the fists.

A more clear config would be nice.
The REwired config for the plasteel fist describes an 'emulated tool'. Which is great if you know how to format an id. It would also be very easy to emulate a modded tool of a higher mining level if so desired. Although that would probably make them too overpowered.

A description of what the the numbers mean could also be good. I think it would be less complicated for people new to modded minecraft.

I"m still unable to reproduce, there's probably another mod interacting here.
Also, what version of forge are you using?

So I also attempted to use the reinforced fist and it seems to harvest diamonds despite the description saying it should actually be unable to do so. The default harvest level is 2, but last I checked that is indeed the same as an iron pickaxe. So either the default config is wrong, or the description is wrong. I changed the config value to 1 and was unable to harvest diamond ore, which matches the description.
The actual values for harvest level should be 0 for wood and gold, 1 for stone, 2 for iron, and 3 for diamond pick levels.