I'm not super familiar with on-chain gas prices, but I thought they were treated using the and logic. So if I have a min gas price of 0.01udsm,0.01ustar then to properly broadcast my transaction I have to pay fees in both tokens, and not either one of the two. Do you have any link for this to be checked out that we can paste here to remember this in the future?

They are treated as or, so one of tokens reaches the min fees can broadcast properly, say, to send the message with 100 gas via the node with 0.01udsm, 0.01ustar min gas prices, 1udsm or 1ustar can pass the check.

Here is the reference:
https://github.com/cosmos/cosmos-sdk/blob/release/v0.47.x/x/auth/ante/validator_tx_fee.go#L38

I'm not a big fan of this approach. Instead I think it would be better to:

1. Add another param inside the NewSubspace function to specify the fee tokens when creating the subspace. This is going to be useful when exporting/importing the genesis as well as inside tests.
2. Rename this method Update as we have done with the Post and Attachment type, to keep everything consistent.

Also, I'm doubting whether AllowedFeeTokens is the proper name. I think AdditionalFeeTokens might be better instead. The name AllowedFeeTokens might make people think that if I specify 0.01ustar then the star token is going to be then only one allowed, while the udsm should always be allowed anyway. Using AdditionalFeeTokens might make everything more easy to understand.

I see, I use the SetAllowedFeeTokens since adding another param inside the NewSubspace will break hundreds of existing test codes, but yeah, it is better to have an additional field.

strongly agree with AdditionalFeeTokens is better.

Finally, I used sed to add the new parameter quickly:

#!/bin/bash

dir="./x"

find "$dir" -type f -name "*.go" | while read -r file; do
    sed -i -E ':a;N;$!ba;s/NewSubspace\([^)]*time.UTC,/&\nnil,/g' "$file"
    echo "$file"
done

Is any other tools to make modifying codes quickly?

I honestly don't know of any other tool that can easily update the code. I would have done it by hand 😓 Great job using sed 💯