Depth is the only thing that decides your price
A pool holding two million dollars a side absorbs a ten-thousand-dollar trade with negligible impact. A pool holding twenty thousand does not. Same token, same interface, completely different execution.
This is why checking depth matters more than checking the logo. A token can be listed everywhere and tradeable nowhere at size.
Fee tiers and what they are for
Stable pairs typically use a very low fee because the two assets barely move against each other and volume is the business. Volatile pairs use a higher fee because providers need compensating for inventory risk. Exotic pairs charge the most.
A pair can exist in several tiers at once; the router picks whichever gives the better net output for your size, which is sometimes the more expensive tier because it holds deeper reserves.
Why providing liquidity is not free money
Fees accrue continuously, but so does divergence loss. As the price of one asset moves, the pool rebalances against you: you end up holding more of the loser and less of the winner than if you had simply held both.
Fees can exceed that loss on a high-volume, low-volatility pair. They often do not on a volatile one. Any yield figure that omits this comparison is incomplete.
Reading a pool before you trade into it
Look at reserves on both sides, recent volume, and the price impact your specific size produces. A pool with large total value locked but a lopsided reserve is thinner than its headline number suggests.
FBT Swap shows the price impact for the amount you entered, which is the practical version of all of this: if the number is large, the pool is too small for your trade.