Combine barriers with suitable access tags and values. For the first one: barrier=bollard + motorcar=private. The open metal bar with motorcar=permissive.

High tide was mentioned somewhere in the wiki as the correct practice and some have discussed how to tag the mean and low tide marks, current best might be
osm.wiki/Tag:natural%3Dwetland

So far adding the traffic_signals is much less important than having the geometry of the crossing ways sufficiently correct. If the signals are just marked on the various crossing nodes, someone can then later use a relation to tell routers about the synchronizations and such about all the traffic signals in one intersection, once someone (else) has proposed an adequate relation osm.wiki/index.php/Relations/Proposed/Traffic_Lights for such use.

Any technical profession and hobby has a gender bias, from devastating to negligible. Be it technical university education, freight transport or car sports, the women are a minority. Of these only car sports attracts female spectators (which could want to try the sports themselves) because the drivers are showing off their sport skills; there's nothing hormone rush inducing in shouting "look at my big map!" (just as "look at me solve this with a 17th order Laurent-series" might appeal only to math professors)...

Also, the male mappers are (for the most part) either outdoor people (hiking etc.) or the geeky type (like me). Most of the active outdoor-hobbyist women are more likely to concentrate on the doing the outdoors part, not on watching and correcting the map. Technically oriented geeky women are such a minority (and only sociologists can try to explain why) that it'd be as probable to find a fairy flying around with a gps.

(I could and should refute the points in the previous comment, except for the first one, but I'll limit myself to the notion that point 7 is definitively solved by photomapping.)

Anyone driving from north to south never touches or crosses the lanes for driving from south to north. There's space in the center of the intersection that is used for driving east-west (and turning), but only because the nondivided road crosses and connects the separated roads. Keep straight roads straight has been in the editing standards as far as the wiki history goes and the recommended practice in all mailing list discussions. If the crossing road didn't exist, there wouldn't be a turn in the separated carriages so there shouldn't be one when the crossing road is added.

And I didn't mean that one should draw each traffic signal pole, but one could. Eventually someone might be adding pedestrian crossings and having the traffic signals drawn as being only after the pedestrian crossing would then seem illogical.

As for the second example I admit that neither is optimal but having both (the non facing) roads drawn straight across the bigger road is IMO closer to reality: driving across the bigger road includes first turning (almost) parallel to the bigger road and only then turning to the other side. At some point when the offset of the non facing roads get smaller it becomes reasonable to connect them directly, i.e. the crossing just south of your example looks like one. A driving direction "drive straight" wouldn't be confusing in that when crossing the bigger road, but the example intersections is more accurately guided as "turn right and immediately left".

1) Do the lanes in the separated directions curve into the intersection? No, everyone drives straight.
2) Do the lanes in the separated directions touch and overlap each other in the intersection? No.
I really urge these should be drawn "as two parallel crossings". Location of the traffic_signals is not yet used for anything and they might as well be added as separate nodes on all incoming ways at the exact point where they are.

You can add a tag 'postal_code' on any street.
The more common/proper/first in the street sign/official name goes in 'name' and the Welsh name in 'name:cy' or the enter the English name as 'name:en' if the Welsh name is the "primary" name. The two letter codes for languages are the same as in some standard. That's how it's done at least in Finland where we have both Finnish (name:fi) and Swedish (name:sv) names for many of the streets. Only what's in 'name' gets rendered, for now at least.