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.