Yeah the plugins you can use are the ones you buy thru Avid Marketplace inside PT First so no plugins you already have will work and there are nothing that will work to get them working.
Also PT First is a free test DAW so of you are going to run very advanced mixing you will need the right tools for the job. You wouldnt show up at a constriction site with your childrens toy toolbox
So if you wanna try the real PT version you can do a monthly subscription and evaluate for a month or two or buy a secondhand license for around $200 and then upgrade to yearly plan when you can for $299
Best of Luck
Christopher