Sorry, but I really cannot advise you on other plugins
However, regarding registration spam, that typically has nothing to do any kind of login widget anyway (spammers typically don’t click on links but attack things programmatically)

What i *can* say is that i killed a lot of registration spam by adding this recently: https://wordpress.org/plugins/ban-hammer/

it’s a bit quirky in places (and somewhat brute force) but in my case it stopped a lot of obviously fake registrations – it’s a start i guess and there are of course 1000’s of other security plugins anyway that [claim] to deal with this stuff too but that’s all down to personal preference and particular setup of course as to what is the right way for you