The reported download speeds vary wildly (from the "normal" limit of 4Mbps to over 100Mbps, which likely won't last), but the performance on all will be improved by the huge gain in latency speed (down from 600ms+ as low as 50ms - the lower the better).
Yes, RCI doesn't have a tier for just email and the lower tier Surf seems to be going away on most ships (not available at all in the planner), leaving only the more expensive Stream tier as the only choice. If you only need check occasionally, you'll probably find free wifi in ports.
Welcome to CC.
Only you would know your drinking pattern - the break even for you would be about 7 drinks/day (2 free+5 from drink package). Unless you know for sure you'll drink that much (somewhat unlikely on a Med cruise), skip the package and buy a la carte.
That varies by the drink, from a low of ~$3 for sodas to $8+ for other types - the break-even is usually about 3+ of the more expensive drinks. The app may list the prices for some drinks under some of the bars.
In the latest SEC filing, RCI mentioned that it has a planned 30-35 year useful life for their ships, so like Grandeur, many of the older ships will just soldier on with little to no upgrades (the money for those will go into ever more expensive required maintenance).
To be fair, even when they had them, the printed bar menu hardly included all the drinks on the "menu" and I'd venture to guess few land-based bars have full printed drinks menu either.