Will extending my 30-day visa exempt at IT Plaza impact my Non-O visa application later at Chaengwattana?

Go take the regular 30 day extension on your 30 day visa exempt entry at the office at IT Square Laksi,

THEN

go and apply for the 90 day non-O visa based on marriage at Chaengwattana at Counter C-1 for 2000baht. Keep in mind there is NO seasoning of the funds required for the Non-O visa. 🙂

You only need a minimum of 15 days left on your current stamp (30 day visa exempt or an extension from it) to apply for the in country Non-O at C/W.

The seasoning isn't in place until you apply for the year AND after you get the Non-O 90 day visa and run the time down the funds will be seasoned enough

No problem at all. The temporary office at IT Square Laksi Plaza is a part of the Bangkok Immigration office at Chaengwattana, same division, same sub-division.

Not sure what kind of effect you think of, but it is a normal procedure to apply for the 30 day Extension of Stay based on tourism or even the 60 day Extension of Stay based on visiting family to get time enough for the 2 months seasoning of the banked money.