Those rule are nice. It used to be possible to travel from switzerland to bodø in only 2 travel day, but since the night train (from trondheim to bodo) disapeared, it isn't anymore.
This is just an example to show that you should check your route before choosing how many days you want to buy

Interrail is often the cheapest way around if you haven't booked in advance.
But if you book in advance, trip beetween a german train station and a station within a neighbouring country can be had for 36 euros. So you could possibly get a ticket from your western residence to travemünde and then a boat ticket for cheaper than an interrail.
But if you want a flexible travel without the expense of having your own vehicle, interrail are unbeatable.
Interrail would allow you a detour trough switzerland .
Edit: from what i see, the border are still anoying by train due to the baltic network being moscow centered.
The warsaw talinn line will really be a great thing!