Underneath "trc20 vs bep20" sits one idea: the coin is the same, the road it takes is not. USDT TRC20 is the version of USDT issued as a TRC20 token on the TRON blockchain, and it is one of the most common ways to send USDT because fees there are usually low. The same coin also exists as BEP20 on BSC and as ERC20 on Ethereum. Each version has its own fees and rules, and a balance on one network never moves to another on its own.
TRC20 vs BEP20 is mostly a question of chain and fee coin. TRC20 runs on TRON and pays its fees in TRX or through energy and bandwidth; BEP20 runs on BSC and pays them in BNB. Both are usually cheaper than Ethereum. Which is cheaper at a given moment depends on network load, the resources an account holds and the withdrawal charge an exchange adds. TRON addresses begin with T and BEP20 ones with 0x, yet the network should still be picked from the list at both ends.
What is the BEP20 network? Strictly, BEP20 is a token standard on BSC rather than a network of its own, though wallets and cashiers list it as one. USDT BEP20 is the version of USDT issued under that standard, and its fees are paid in BNB, the native coin of the chain, usually at low cost. Addresses on BSC start with 0x exactly as Ethereum addresses do, and one address can exist on both chains. The look of an address therefore never shows which network a payment will travel on.
Ethereum and compatible chains share the same address format, so one 0x address can exist on both while the balances on each stay separate.
Not reliably. Addresses on BEP20 and ERC20 share the 0x format and may match exactly, so the network is picked from the list and matched on the receiving side.
A small first transfer costs one extra fee but shows that the network matches before the full sum moves.
Its network list for sending and receiving should name TRC20 or TRON explicitly; supporting USDT alone says nothing about the network.
ETH, as gas: the gas the transfer uses times the gas price at that moment, which rises when Ethereum is busy.
In energy and bandwidth, from resources the account holds or has been delegated; when those run short, the network burns TRX to cover the difference.