It can be done but it's tricky if you don't know what you're doing. I prefer to use Sukritact's Gold since they have updated for Monopolies and Corporations, which required deleting the RESOURCE_AMIFTGOLD from the mod files and changing the Mountain Mine valid resource to RESOURCE_GOLD instead. I ended up using AMIFT's gold icon to replace Sukritact's icon (I like it better) by adding a higher load order to AMIFT and using Replace instead of Row for each altered RESOURCE_GOLD icon in the AMIFT_IconDefinitions.

Going even further, I prefer the goats from Sukritact's Resources so I modified them to spawn on mountains and have hamlets use RESOURCE_SUK_CHEESE, deleting the RESOURCE_AMIFTSHEEP completely from my mod. Haven't gotten around to changing the cheese icon yet though, lol.

Hey Ciar, not sure if you're still floating around, but can I please clarify some of your instructions? (as well as make it more clear for future people)

So Using notepad ++, open the mod folder at steam/steamapps/common/workshop/289070/2218997774

I don't know what you're referring to with " deleting the RESOURCE_AMIFTGOLD from the mod files". What mod files? all of them?
There's no RESOURCE_AMIFTGOLD in the folder, and searching the folder for that links 4 files. AMIFT_IconDefinitions, AMIFT_MountainImprovements, AMIFT_MountainResources and Resources.artdef. I'm not sure if you mean delete all of the lines in all of these? And if you do, does this step need to come after the next with about changing the valid resource type, as that line is one of these?

In AMIFT_MountainImprovements.xml I can change the line with Mountain_Mine valid resource to RESOURCE_GOLD, but is there anything we need to do with the next line regarding just a normal mine? Does this need to be deleted or changed to RESOURCE_GOLD as well?
<Row ImprovementType="IMPROVEMENT_MINE" ResourceType="RESOURCE_AMIFTGOLD"/>


With the load order, where do you add the load order? Under assets in this mod, higher than suk's 1, or do you add it under properties at the top for both mods?

In AMIFT_IconDefinitions, do you use the Replace instead of Row for each altered RESOURCE_GOLD icon in the AMIFT_IconDefinitions for 9 lines, 6 unter icontextureatlases, and 3 under icondefinitions?
Also in icon there are code like "ICON_ATLAS_AMIFT_GOLD_RES", "ICON_ATLAS_AMIFT_GOLD_RES_FOW" do these get changed?