Swapping USDT for TRX
Most people looking to buy TRX are not investing in it. They are trying to unstick a USDT balance on Tron, because an ordinary wallet will not move it without energy, and energy comes from TRX. If that is why you are here, you can stop: this wallet pays that toll out of the operation.
100 USDT 
TRX What TRX actually buys on Tron
Tron charges in energy and bandwidth. You get a small daily allowance, and past it you either freeze TRX to generate more, burn TRX outright, or rent energy by the hour from a third party. All three are the same purchase wearing different clothes: TRX to be allowed to spend your own dollars.
When buying it still makes sense
If you hold TRX as an asset, or you use Tron through other wallets that do make you pay the toll, then a swap is a swap and this is where to do it. The quote is the raw route with the network fee inside it.
Prices move, dollars do not
Swapping USDT for TRX is not a transfer between two forms of the same money. It is an exchange between a stable asset and a volatile one. What arrives is priced at the moment you sign, and it will be worth something different tomorrow.
The rental market you are avoiding
Energy rental exists because Tron made a market out of a technical requirement: someone with frozen TRX sells you their allowance for a few hours, priced by demand, through a service you have to find and trust first. It works, and plenty of people use it daily. It is also an entire errand standing between you and sending your own money.
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Several wallets in one account, unlinked on-chain
Hold as many wallets as you need inside one Telegram account. Their addresses are not linked on-chain, so paying from one tells nobody about the others. Send to a @username or to any address.
Questions
Do I need TRX to send USDT on Tron?
Not in this wallet. Energy is paid for inside the operation, which is what removes the rental step entirely.
Should I buy TRX for energy anyway?
Only if you use Tron through other wallets that require it. Here it buys you nothing you do not already have.
Is the amount I receive fixed?
It is fixed at the moment you sign, at that moment’s price. TRX is volatile; USDT is not.