From my understastanding ( I'm no lag expert )

Ms stands for the amount of milliseconds that the signals your device sends and receives back from the server.

The higher your ms means the longer your device is taking to send those signals and receive them back , this is why some countries naturally have a higher ms as they are further away from the sever therefore take a little more time to send and receive those signals. This in turn creates delay and I don't think there's any fix for this , bigger companies and games will often have different servers based on contenents / counties to eliminate as much delay as possible for the best plyer experience , however for this to happen there must be a big enough players base as this separated players from playing with people from areas who connect to different servers.

Now lag is when the ms is not stable , this is what causes lag and people teleporting to places. This is at most of the case your fault , might be that your device is simply too old or your router is damaged / not functioning properly. Therefore your router will take different times to send each individual signal which causes spikes.
For an example your router could be doing : 100 ms , 104 ms ,102 me ,99ms and all of a sudden 250 ms which is a big difference in timing and would cause a spike. This is often a problem on your end but can also be the servers end if it's overfilled ( which in case of grasp it often is )

Someone who lives abroad might have an ms of 200 or even 300 but this doesn't mean they will nevesarraly lag spike , they will delay yes, but that's because your ms and their are different and if they delay to you , you most likely delay to them so they don't have an actual advantage , it's just that their already used to playing against delay whereas most people ent. If they have a ms of 230,232,240,235 they won't actually lag spike

Sorry if this is a bit complicated but that's my understanding of it which may in fact be wrong but that's how I've always looked at it, that why you'll often see me defending the delay side in the arena.

An easier grasp to picture this could be in terms of boxing, there are two main stances which are southpaw and orthodox.

Orthodox boxers are the most common ones so they are used to facing each other , therefore when a southpaw comes in they aren't used to it as it's not common for them which might give them a bigger challenge
On the other hand southpaw boxers are used to fighting orthodox boxers therefore it's not as big of a challange for them as they experience it more however the level of skill might not be that different.

It's kinda the same with players with highly constant ms vs low constant ms
Low constant ms is more common therefore they'd are used to fighting low constant ms
High constant ms is more rare but they always fight low constant ms players so they are more used to dealing with that delay whereas others wouldn't be.
I'm quite good vs people who delay in my opinion, the only way to overcome it is by trying to soar people who delay more often so you can get more used to it

Again I'm writing this on my phone and it will probably be a big mess but I hope it helps you in some way or another. However to end my point it would be unfair to cap soar rooms to ms values as it would bassically a form of discrimination to players from other countries as they really aren't at fault for their high constants ms