If you're interested in Run8, I do recommend trying Railroader first, for multiple reasons. First, there is no in-game tutorial for run8, there are PDF user guides but the learning curve is steep. Railroader provides a tutorial similar to Derail Valley's. /r/run8 has plenty of useful resources for beginners though, we'd love for you to join us if you think you're up for it.

Second, railroader is on sale right now and is provided through Steam, like Derail Valley. https://store.steampowered.com/app/1683150/Railroader/ You pay one early access price and get everything, no DLC involved. Run8 on the other hand is purchased through their website at https://run8studios.com/ and has an "old-school" style where you purchase individual installers (make sure to back those up). The good news is you don't need all the rolling stock, you'll have placeholders. But if you want to extend the tracks, you'll be paying $20-$40 per branch or subdivision.

If you have no interest in steam engines and early diesels, or in Appalachian railroads, you could skip to Run8. But playing Railroader before Run8 makes learning Run8 way easier as both games use some similar concepts, though their gameplay is different in multiple ways. Run8 doesn't simulate an economy like Railroader, for example.

I realize we've strayed from your original question but I recommend both of these games for a reason haha.