Two part reply here.
First on the admin and distribution fees. If on the easymax rate the admin fee matches the rro rate. If memory serves the rro admin fee is regulated but I am not 100% sure. All the fees below the delivery line on your invoice are set with regulators and will be the same no mater what provider you go with as they are from Enmax Power not Enmax Energy.
As for whether to still go with fixed over floating. Its a gamble either way. Personally I'm staying on the fixed rate. Having looked over the last few years, there have been times where it was lower for a mth or two but over the 6 mth period or 1 year period the fixed rate ended up being better.
Looking online at
http://www.ucahelps.alberta.ca/price-summary.aspx will give you all providers prices. Since every providers fixed price is higher than Enmax's I worry about going to floating rate as I don't know if Enmax's will go up or not.