You might ask: If version 1.47 or 1.48 exists, why hunt for 1.45?
The ETS2 modding community is very active. Most high-quality mods (truck mods, map combos, sound packs) are updated for the current version of the game (currently version 1.50+). If you stay on version 1.45, you will be restricted to mods created in 2022. You will not be able to use the latest truck models or graphic mods.
Base game + all map DLCs ≈ 12GB. Adding free mods like Promods adds another 8–10GB. Expect up to 22GB total.