Safety: Mains step down transformer vs SMPS for bench power supply?
Look for a CE marking, or its equivalent in your country. That indicates the transformer or supply has been designed to an appropriate safety standard. If it's marked, it should be OK, if not, then it won't, regardless of whether it's a transformer or SMPS.

What a mains-connected piece of equipment must do to gain such a marking is to have adequate isolation between input and output. This means the transformer must use insulation between the primary and secondary, and must have adequate clearance and creepage distances maintained for the terminals.