paper or glass plates for cocktail hour?

It depends on the venue and/or the type of wedding setting. If you are able to afford the glass plates; use them. If the wedding is a very formal wedding, use the glassware. If you are in a casual setting like a outdoor family style barbecue, paper may be admissible. If cocktail hour poses a financial strain, opt for nuts or light finger style foods and a beverage; or simply eliminate it and give a start time for the reception.

If you are going for disposable, here is a previous thread that might be helpful to you.

https://www.weddingwire.com/wedding-forums/plastic-cups-and-plates-that-looks-real/aa48eae084530339.html

Best wishes.

Really depends on the venue and the style you are shooting for. When in doubt go for the clear heavy plastic.