If you are saying that, as you type text into the posting ‘window’ there is a significant delay before the text appears, that doesn’t happen to me. What I type in appears instantly and that is the case whether I’m using my iMac desktop machine (with a proper keyboard) or my iPad tablet’s virtual keyboard. My broadband speed is reasonably quick (around 40mbps download and 18mbps upload) but I doubt that broadband speed will be the culprit.
As the issue evidently did not occur for you with the ‘old’ forum, and nobody else has mentioned your current problem (yet), I suspect that it’s not the new forum itself that’s producing the delay. It’s possible that the marriage between the software on your tablet and the software of the ’new’ forum is not a happy one, and perhaps security/anti-virus software you are running is the cause.
You might try experimenting with a different browser to see if that helps - otherwise (if your problem is widespread) the forum’s Administrator will need to investigate.