Note - these are current values, and may change until release.
ERC20 Tokens
ERC20 compliance: pool tokens should generally be ERC20 compliant, though it is more flexible than V1 in some areas (e.g., it does not check for bools for transfer and transferFrom). There are no upgrade mechanisms in the contracts to allow for token upgrades. Any upgrade will need to be manually coordinated and moved into new pools.
Tokens that have internal transfer fees or other non-standard balance updates may create unexpected arbitrage opportunities. Ex: DGX has both a demurrage and a transfer fee that will change a pool's balance compared to the internal accounting balance. These must be handled through special pool logic on V1, and are not supported on V2.
Minimum Bound Tokens - 2
Weighted and Stabe pools must contain at least two tokens.
Maximum Bound Tokens - 16
The maximum number of tokens that can be in a given Weighted pool is 16. Stable pools currently have a practical limitation of 4, but this is still in development. There is no theoretically limit on the number of tokens new pools can support - though the math (and block gas limit) will impose practical restrictions. For instance, the Weighted Pool math imposes an upper limit of 100 tokens.
Maximum Swap In/Out Ratio - 0.3
A maximum swap in ratio of 0.3 means a user can only swap in less than 30% of the current balance of tokenIn for a given pool, or swap out less than 30% of the current balance of tokenOut.
Minimum Swap Fee - 0
It is possible to have a zero swap fee on V2.
Maximum Swap Fee - 10%
This is to prevent malicious pool controllers from setting predatory trading fees. (For instance, a pool controller could front-run a large trade and set the fee to 99%.) No one wants to be this guy. Note that V2 also charges a protocol fee, up to 50% of the pool's swap fee. For instance if the pool swap fee is 1%, and the protocol swap fee is also 1%, the total fee paid by the trader is 0.01 + 0.01 * 0.01 = 1.01%.
Minimum Balance - it's complicated
This is done differently in the V2 math. Balances can't be zero, but the mechanism keeping them non-zero is different - mainly burning a small amount of the initial BPT on creation.
Min/Max Initial BPT Supply - it's complicated
The initial supply is computed in the new V2 math, and is not passed in by the user. The protocol also burns an initial amount to prevent rounding/boundary issues.