Generic question about making roads, crossings...etc

I have a few generic questions about building a map.

So, in most cases map builders place the sidewalks and then add polygons to make the road. Sure that's a very precise way, but what about making road splines and crossing objects, like in OMSI?

I want to start to build a real map but I have concerns about it.

If I built it with road splines and crossing objects (note: almost all of the crossings look exactly the same), it'd take maybe a few hours to build kilometres of the map. But if I had to place the sidewalks on their own, measure the distances, add polygons in all crossings and streets, it would take days and it would not look any better, since almost all of the road crossings are the same (simple 90 degree crossings with the same amount of lanes).

So, is there any benefits to not build a map like this? Like how the ligths work on polygons and/or scenery objects...etc.

As a newbie i'd say it shouldn't make any difference. For example to build a bridge you'd place bridge splines and place the bridgeheads as objects. And it shouldn't make a difference there, so why would it anywhere else?

By the way, is there any method to rotate an object precisely? Like not with moving the mouse after pressing R but typing a number how many degrees rotation (according to I don't know, some global variable like the tiles as in OMSI).

One thing came to my mind. Are the footprints for only informing purposes or will they have any feature when AI comes in?

I mean for example I made roads with sidewalks in one spline. I marked them as driving durface. May this occult in any problem or error in the future?

Also, should I worry about these terrain holes?

The funny thing is that they appear next to straight sidewalks and not around the sharp "sidewalk islands". Once it was mentioned in the lexicon that we shouldn't worry about these, because it's a well known bug. Sooooo, what should I do abaout these? I thought something like placing a road textured plane (scenery object) at -0.01m so the actual wholes couldn't be seen but that not-so-sophisticated method won't solve the terrain coloured areas.

I know they're there because of the algorithm. Placing the polygons the other way around etc doesn't help, I tried with many forms.

I'm just asking whether this is "normal" with this terrible terrain generating method or I'm doing something wrong in the editor.

Another issue I recently have is something like this:

I tried to make the start of a bridge (I know we can't build bridges at the moment). I placed some subgrades as you can see. But it doesn't work at all. Parts which should be flat have hills on them, parts which should gradiently rise are flat. What am I doing wrong in the editor?

After all I could "solve" this problem, by placing a road spline which effects the terrain. And after that I'll place the sides of the "bridge" as standard splines, so I'll have something which looks like a wall rather than a hill.

By the way, is there any warning why I shouldn't build a bridge from standard splines (bridge spline) and the S49 rails which do not effect the terrain? I heard that rails above each other doesn't really work at the moment, but that's particularly not that important for me.

Well maybe different running sounds in vehicles, but I guess that will be linked to the rail type anyway.