Q5: Bgr-hardly-certainly not if several other Balkan/East EUR towns are in your list already. Its reputation among young travellers is mostly for its hedonistic summer-nights binge&booze nightlife. It has some brutalist socialist style concrete monster-buildings as being main capital of proud Yugoslavija in Tito´s times-since then the country fell apart in pieces.
But it will be very hard to impossible to avoid it for any of the longer trips you mention
Sj+Ms(thats only that famous bridge); More interesting, but need long (8-9 hrs) BUStrips getting there and away anyway. ( from Bgr, to Zag). Though there is the odd train in Bosnia-forget that for pracitcal reasons-its a minor tiny niche only for dedicated ´onlyonrails’typos.
Re1-first: there are 2 major lines HU-RO: 1 is for some weeks out of use now-or maybe just finished, due to works/repairs, but in summer it should all be back to normal in renovated state.
Re 3-first: most likely to bridge that gap it is a short sector of the direct bus Sof_Thess-making you loose many hrs in waits on those unattractive minor stops and even finding the stops of bus&train-perhaps KMs apart.
Direct Sof-Hrvatska: fly, WIZZair is the RYAN of East-Eur and in general much, much nicer, but with the same tricks re luggage&extras. (easy to avoid on their app-most often I fly light for <20€, but without bekpek). If willling and able to commit yourself monthes before-probably even cheaper as the 2 long bustrips together.
Using your pass-you have paid for it anyway: be creative and use the 2 ways on train that now exist RO-BG: via the Vidin bridge-into RO (Craiova, once the seat of the DaCia ugly-worse car, now of Renault I think), then to south HU (via Timisoara-inviting you to visit some areas away from those capitals you listed before.
IF still vying for the way via B-gr: as said so many times before: seat61.com is dedicated to as much on trains as can do and with various tips on how to shorten bustrips-and lengthen total trip time by switching to train=voz as soon as can do. But I think doing Bgr->HRvatska even needs a taxi for some 20-30 KM-s-dedicated railfans spare no expense in fulfilling their dreams. (I did it on the through train Greece-Zagreb (train on to MÜnchen) many moons ago without much trouble, thats long ago.
Germans can also in their drive for ´überpünktlich´ be very knowledgeable in such trivial facts, plus that there are so many of them. I read all forums I know of near daily, rian does that too, so together with the others we trust to have enough current knowledge.
Q.5 I personally can handle long bus journeys but the person I’m coming with cannot - on occasion the 1 long bus journey is acceptable if necessary but for the most part it is not a valid option.
- Is Sarajevo & Mostar worth a visit?
- Is Belgrade worth a visit?
Q.6 By best I mean length of time.
