The exchange that your order can be filled earlier are exchanges with high trading volume of the listed coin. With what you have explained, it is better to go for Kucoin.

Do not follow the low price, what if your order is not filled earlier and no buyer or seller at the displayed amount of the limit order, but just in a way the market order of the coin will not favour you, then you might even end up buying at higher price or sell at lower price. Low volume can be very frustrating.

The lower price seen can be deceiving which is most likely what will happen.

The thing is they might cancel their order and there's a chance a new seller want to sell large sum with lower price too. I don't know which coins you're talking about and how they're interested with Gate.io rather than Kucoin while the volume Kucoin is far higher than Gate.io... You'd better checking the buy and sell order on the next hours and next days, if the volume is still higher in Gate.io then use Gate.io

Does this coins doesn't get listed in Binance? Binance should be the highest volume trading.

firstly it does not and will not affect developers or pools or node users. (just doing those tasks*)
its a bill that affects custodian services/money services businesses(MSB)

it will on the small businesses that do coinjoins,escrows, custodian services, etc make then have to do more bureaucracy. but on the flip side if they run a legit business and can invest the time and money they can prospoer into being a business that has consumer protections like insurance to protect users value.

big businesses that are already legit dont need to change much as they already KYC customers.

with more businesses able to operate a legit operation which has consumer protections, it can cause more people to want to invest in crypto via these legit services.

the downsides as just breifly hinted is that small businesses that dont bother/didnt comply with certain regulations will need to start doing so
so expect things like other network 'bridge' services that offer fund transfers to need to up their game to stay legit.

dont worry about software developers or pools needing to KYC.
*however if those individuals also have a side hustle such as them being the 'federated' co-signer of locked up funds(custodian) then they will need to make themselves an official MSB for their custodian activities of holding users funds for the purpose of transfers
this also includes things like LN routing, (if LN ever got to a stage of transfering larger amounts more then pizza money)

this means small hobby routers that are trying to make sub-pennies per transaction for pizza money may not have to worry.. but they wont really survive in legit transactions of large amount as routes/transfers would require some KYC stuff happening on larger amounts, which involves centralising and turning routers into official businesses.

you may see some 'honeypot' traps occuring where officials do large trades to catch unregistered routers allowing large transactions. as what happened in a few cases when the bitlicence became law.

but if those wanting to be ethical service providers of large amount custodian/transfers. and are able to register as a MSB. their business, then official can prosper immensely by offering stuff the blackmarket people cant offer.