I will be talking about 1v1 balance since its hard to balance both at the same time..
About Iro : I think iro doesnt need a nerf at all. It is quite strong at some situations with good treasures but a nerf would possibly make them bottom tier.
Japan : This civ feels really weak against Rush civs/semi FF civs/timing push etc. I think reverting Pavillion nerf would be a good fix, if not possible, go for discount to consulate probably ( 150w maybe? ) or make shrine buff significant eventhough Japan doesnt struggle with eco, imo reverting Pavillion nerf makes more sense.
Otto : Otto feels quite strong at some MU's because abus guns are quite strong with 20 range and it's a big deal for most civs, only mu Otto loses hard is against germany but I think thats not very important since germany is one of the best civ anyway. On the other hand, Otto is still one of the worst civ on no tp maps. For the record, abus guns rekt goons hard now which is also problem. I think as dia mentioned above, moving 20 range abus upgrade to age IV and giving otto some more options on no TP maps are probably the best deal.
Aztecs : I dont think aztek is that bad as dia mentioned, however they deserve a buff but since I don't play the civ, Idk what to suggest.
Spain : They got buffed but I think ff is still weak against some civs. Nilla Spain had some nice exp boost, would be good if it would be implemented to EP Spain.
Dutch : %100 agree with dia
France : %100 agree with dia
Germany : agree with dia
Brit : agree with dia
Russia : I disagree with reverting musk "buff", because it isn't even significant at all.
Porto : I think we miss the part that goons are the key unit of Porto, same goes for Sioux they have best cavs but their skirms are quite weak. I think instead of thinking how to buff cassadors, we would revert goon RR nerf for ports to %25. Also giving 100f crate back for 95f vills will be quite reasonable since you can't 10/10 anymore which was quite strong strategy on RE. Additionally, Mameluke werent nerfed accordingly,as @
n0el stated before, either 1250 coin for 5 Mameluke or 4 Mameluke shipment for 800c will be more fair, I personally would rather 800c 4 mameluke shipment.