Do I need a step up transformer for a residential installation or will a TL inverter do?
I think you’d be hard pressed to find a residential inverter with a transformer these days. What brands are you comparing?
All modern solar inverters use a transformerless design due to the low cost and high efficiency. The inverters operate with a wide PV input voltage range usually from 100V up to 600V DC.
Transformers are only really used these days in the more powerful off-grid battery inverter-chargers which need to power appliances with high surge loads.
The benefits of using a transformerless inverter are that it’s much lighter in weight than inverters with transformers, it offers higher efficiency ratings and it’s also capable of dual MPPT inputs, but it depends upon manufacturer.