One of the weaknesses or difficulties in how this question is phrased is its insistence on Western Europe in the seventies while trying to focus on Austria and Switzerland as well.
The problem there is that both countries were not members of the European Economic Community in the 1970s resulting in basically bilateral agreements and treatise for every neighbour of Switzerland and Austria to be considered mandatorily.
That means 5 agreements for Switzerland with France, Germany Liechtenstein, Austria and Italy. This also means 6 agreement and conditions to list for Austria with Germany, Chechoslovakia, Yugoslavia, Italy, Liechtenstein (and Switzerland again, covered by the first list). Both lists covering 10 years is quite broad.
It seems pretty clear that the borders between Belgium, Netherlands, France, Luxemburg and Germany were already pretty easy to travel across. While in times of heightened terrorist activity, like 1972, border and police controls in Germany were expanded across the board (cf Fahndung and Schleierfahndung) that doesn't really mean that the borders were completey shut tight. The RAF terrorists transported the first captive then dead Hanns_Martin Schleyer in 1977 apparently across all these borders unimpeded and with a comparatively low risk of discovery. This is evidence that any border checks were at best random. Some checks were also so relaxed, not in the least because some borders were also so ridiculously drawn between Belgium (example: Vennbahn), Germany and the Netherlands, that many locals crossed these routinely several times day, for example to go by their agriculture businesses while never subjected to any control at all.
Crossing the border into Austria or Switzerland from Germany was far more complicated and closely regulated, generally. If traveling by train it would stop before the border, then you would have been told to show your ID or travel pass, and you may been subjected to random searches for contraband or smuggled goods. Traveling by car it started to depend on where you were crossing the border. Large crossings being a major stop gap with a similar procedure like with going by train.
This was all quite different if you chose a remote crossing by car. Sometimes you would notice that all of the sudden the road marking and street signs were subtly different and you were now in a different country. This was even less pronounced when crossing the green border, since this was patrolled at random but without a fence or wall.
There were generally no visa requirements at all. But it was not a minimal amount of money required but to the contrary: a maximum amount of money to bring in was allowed. Since every country had its own currency, in order to avoid currency speculation and tax evasion these amounts for money allowed differed enormously over time and was different for each country.
Keep in mind though that there was a enlarged special customs zone (Zollgrenzbezirk) around 30 km inwards from the actual border where you could have been subjected to just the same controls at random like at the actual crossing.
A joke from that time illustrating the green border between Germany and Austria went as follows:
A Bavarian border patrol finds a hanged man in the forest. Apparently suicide. Trying to avoid all the paper work that would ensue they come up with the idea of cutting him down and rehanging him on the Austrian side of the border, making them do all the paper work.
They do so.
A few hours later an Austrian border patrol finds that suicide on their side of the border. Says one of the Austrians to the other:
"Oh my God, look! He's back up there again!"
