I am new to Train Sim and was wondering, do you have to have TS 2021 to buy routes such as the Welsh Marches Line or can you use an older version such as TS 2018. (In case you are wondering I bought TS 2018 off steam near the time that 2019 was released because of the fact that it had the north Wales costal route however my laptop didn’t have nearly enough power to use it so I gave up however I am getting a new laptop hence the question asked).
You don't have to buy the latest version, no. So your TS2018 will update automatically to the TS2021 core of the game (or whatever is the latest version when you read this: TS2022 is being released shortly). You don't get the routes that come packaged with TS2021/2, just the core of the game updated. All routes will be compatible.
When you get your new Laptop install Steam and everything you have already purchased thru Steam will be downloaded to it. Any third party add-ons, repaints, scenarios will need to e copied from your old laptop. Most of us back up their Assets and Content Folders to a portable Hard Drive - a 1Tb should do https://www.argos.co.uk/search/port...533/storage-capacity-(gb):1tb/opt/sort:price/ Peter