People in Sweden (and most of Western/Central Europe for that matter) generally speak very good English. I honestly don't see how a language barrier could become a problem at all. At least not for something as simple as doing a soundcheck and connecting a DI box. The ONLY Western/Central European country I've ever had any problems whatsoever communicating in English is France, and even there it's ok most of the time. In some (but not all) East European countries it can sometimes be a bit more challenging, but people working at live venues will generally speak decent English all over Europe.
With your setup the difference between the JDI and the RNDI is pretty much negligible from the FOH engineer's (or the audience's) perspective. If anything, the question you could perhaps ask yourself instead is whether you should use ANY of these two DI boxes, or a different DI box altogether. Both the JDI and the RNDI have a rather low output. Live sound engineers are typically used to DI boxes with a significantly higher output. This shouldn't matter at all as long as the mixer has decent quality micpres (and at venues in Europe they generally do). Still, if your objective is to make the job easier for the FOH engineer, you might want to consider using a DI box with a more "normal" output for live sound, but I really don't think it will matter at all.
As for active vs passive, all the most commonly used DI boxes for live sound in Europe are active. Phantom power won't be a problem. I have NEVER played a venue in Europe that couldn't provide phantom power for a DI box. In fact, if I personally had to choose active or passive for a live gig I would go active, because it's usually the allround safest choice. But I never actually have to make this choice because...
...I never bother bringing a DI box to a live gig at all anymore. I've played lots of gigs all over Western/Central Europe and I have never, ever needed to bring a DI box. The venue has ALWAYS provided plenty of good quality DI boxes. Typically BSS, Countryman or (pre-Behringer) Klart Teknik. All very good DI boxes. Will they sound the same as a JDI/RNDI? No, they're slightly different sounding, but not better or worse, just SLIGHTLY different. Will the difference matter? In a studio/recording setting, sure (although rather marginally). But at a live gig... not at all. No-one in the audience will hear a difference whatsoever.
It would be almost unthinkable for a decent venue in Sweden to not provide enough DI boxes for the entire band. It would be comparable to a venue that doesn't provide mics for the vocals/amps/drums. If anything, FOH engineers will probably prefer using DI boxes they know and trust. In my experience FOH engineers will nearly always prefer using the house DI boxes and tend to give people funny looks if they bring their own. If you're in doubt, check the technical specs for the venues. I'm pretty sure they will have plenty of DI boxes.
If you're using the house backline you might even find a DI box already connected and waiting for you on stage when you arrive. Changing to your JDI/RNDI will then just be an unnecessary distraction and a waste of time from the FOH engineer's perspective.
You can expect decent venues in Sweden to have professional FOH engineers, rather just "some guy" who doesn't know what he's doing. It will depend on the venue though. If it's small pub/cafe type of gigs, all bets are off, but those are the kinds of gigs where there might not even be PA (except for the vocals) so you wouldn't actually need a DI box for the bass. Anything from small club venues and upwards should have a sufficient number of good quality DI boxes and a decent, English speaking engineer.
If it was me, I would leave the JDI/RNDI at home and use the DI boxes provided by the venues. Less stuff to carry around and less stuff that can get stolen.
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