A DBT is strongly recommended. I use only a variac and a current monitor (which I monitor closely but is probably not as obvious as a bulb glow, but I see fine details in current draw that help me trouble shoot and analyze) but this provides no current limiting beyond blowing the variac fuse. A DBT limits the current if your gear has an issue causing it to draw unusually high current (such as a supply rail shorting to ground via shorted outputs)... and if you physically are somehow a part of the circuit that could save your life. Another option would be an isolation transformer but that is more expensive. if you work mainly on solid state gear, a DBT is the way to go, if you work on tube gear sometimes I reckon a variac + dbt.
About the caps, I agree with all John said. I like the nichicon over the elna but as John says it might just be a matter of settling in or personal preference. Also, as you get use to reading schematics you will get use to spotting which caps are in the signal path; on one board in the signal path, you will still have caps not in the signal path here and there. Selection of caps for signal path is quite different to power supply and so on so it's good to spot the differences. You will see folk use audio caps on power supply all of the time, whereas you can get much better caps for such roles.