I haven't noticed any lag out of the ordinary. But there can be DDoS that attack specific routes, causing some players to be affected but not others. This is achieved by them not attacking SE directly, but a route that a lot of players connect through.

Another thing that I noticed was, while a VPN allowed me to avoid a DDoS initially, eventually it caused the reverse issue where the VPN specifically was being rate limited by SE in case the VPN was an attacker, so dropping the VPN stopped my lag.

In regards to the mobile version, the fact is they have a completely different development team, and their team is structured better and setup better to where they don't have all these arbitrary self-imposed limitations, development costs, strict development of what they are asked to work on, and other concepts that hinder raw, passionate development of the game.