Verizon's daily plan is not restrictive at all - it's just expensive. At least, the $10/day plan is. Some people shrug it off - $240 for 24 days (and not charged the days you don't use it) - for one phone, over the scope of a European trip, what's the big deal?
Their $70/month plan is restrictive - only 500MB of data (not nearly enough for me for 24 days - I'd need about 3GB).
I'm frugal, though, and either one would be expensive for me. But I'm also not intimidated by technology.
Last few times, I've used a Dutch Vodafone SIM I bought on eBay. It works in all of those countries you mention. Calling with its limited, though - it's mostly of use for data. Setup of the SIM was easy for me, but there are a few steps - some people might find it too complicated. You have to create an account on the Vodafone NL website and insert the SIM and receive a (free) text message with an activation code to create your account. Then you can add funds to the SIM with your new Vodafone account. (All in Dutch - but if you use Google Chrome like I do, everything gets translated to English automatically.) Then you can activate a "You" bundle, good for a month, the day before you leave for Europe. Your phone should work when you land and turn it on.
My write-up from nearly two years ago should mostly still be valid. Today you can get 6GB of data for 20 euros instead of only 3GB. You'd need to add 20 euros to the SIM using your US credit card, after creating the Vodafone NL account. The SIM itself has no credit when you buy it and costs about $8.20 USD shipped via eBay (currently seller "davinciteam" sells them - never used them).
To make free calls home to the US, even to landlines, you can use the free Google Hangouts app. This has worked well for me for years. (By the end of the year, Google is supposedly phasing out this app in favor of Google Voice, which you can already try.) It works even on WiFi, so you wouldn't need data at all. It can work for incoming calls too, to a US phone number (not your Verizon number), if people need to reach you. Try Google Hangouts before you leave the US, though, so you know how it works. (Probably a lot better than you think it does.)
To call people in Europe, you can probably use WhatsApp (free) which is very popular over there.
Downsides: you won't have use of your Verizon phone number while your Verizon SIM is out. (Perhaps through WiFi calling if your phone supports that, not sure.)
Also, you need to make sure your phone is truly unlocked. Til recently, all Verizon phones were unlocked (not AT&T). Verizon has recently changed their policy. But if you buy the Vodafone SIM and set it up before you leave for Europe, you will find out immediately whether the phone is locked or not. If so, you won't even be able to turn it on with the SIM in place.
