Welcome to Cruise-Chat.
I haven't been on the glass bottom boat but can address the rest. I went to several beaches. Tobacco Beach, and St Catherine's Beach. Both would be not much walking. Elbow beach was more walking. The bus dropped you off and it was a long walk. There was a little shuttle bus though to take you to the beach. It cost $1. This was in 2005.
The soda package is unlimited sodas for one price. (one package per person no sharing). This is for people who drink a lot of soda more than 3-4 a day. Sodas if bought individually are about $1.75 plus 15% gratuity. (unless they've gone up)
Many people that get rear balconies really enjoy them.