Scripts are much faster and reliable. So that's why...
It depends how they are coded though. If an EA is bogged down with features that are unneeded then it will be slower. Or even if it is coded poorly too. Scripts are meant for one-time tasks. After they perform the task, they are supposed to de-initialize and be removed from the chart automatically. Unlike EAs which are meant to run continuously. A script can be made to be stuck in a cycle to mimic how an EA works, but I would not recommend it. Especially considering what you said about switching time frames like you do. Every time you switch a TF, it would remove the script.
I do not think the nature of scripts are faster or more reliable simply because they are scripts. It's most likely your opinion because of using EA's that are 1 of the 2 reasons I mentioned above. If you had an EA coded specifically to do what you say and nothing else, you would see it would work just as fine as a script or even better.
Maybe at least there is an EA that will do the job but won't require to open a new position via that EA ?
What I mean by that is - I open a new position via MT4 but proper TP is set and manageable via recommended EA.
Do you know any ?
I do not know any myself, but I know something like this exists somewhere. It would be faster to code something than to spend time looking for it I think.
You posted another topic similar to this before here:
https://www.forex.zone/ea-modifications/17/close-position-with-define-lot-script/3259There are similarities between both requests. Either could be coded. If you had the choice, which one would you want done?