Alignment tolerances and standards are for the most part left up to the builder. I can tell you that cheap bikes built by the big Three aim for +/- 3mm or .120" and they still, for the most part, go straight enough to be serviceable.

I aim for a +/- .005" in having the bike all in plane and less than .005" of head tube twist over it's length.

The very important thing here is that the BB be faced well so that the faces are parallel within .001". This is perfectly doable with Park hand tools if care is taken. Then you need an accurate and repeatable set up to hold this square BB. If you can clamp the bike down and take a reading and then unclamp it and set it all back up again and get the same reading you are good to go. If you get a different reading on second clamping then you will forever chase your tail.

I'm not at all a 'more tooling is better' kind of guy and think lots of good stuff can happen without real tooling but good alignment is very difficult without good tools.

I hope that helps at least a little bit.

Dave