Call Menu Link inside Component

[Maik]

I have a question about calling correct views inside a component. Assume i have ViewA, ViewB and ViewC. I have SEF and .htaccess enabled. I created a menu entry for CompA. The call to the main site looks like www.mysite.com/compA. If i call ViewB from inside the component the address looks like www.mysite.com/compA?view=ViewB. if i call the main view of the component it looks clean to the menu www.mysite.com/compA.
Questions:
First am i right, that i can only call the views of the component if i have a menu entry for the component? If not i got an 404 error. Next - if i move the menu for CompA to Test/CompA as a Subentry, the link to the view didnt work anymore.

What i use is JRoute::_("compA?view=viewb") now. I search a bit an found this JRoute::_("index.php?option=com_compaview=viewb"), is this the correct way? If i do so the url looks not so seo-friendly and shows the ?view=viewb Option at the mean view of the component.

I am unsure and want to know which the correct way is. If i have solved this i will later use the Routerfunction to create clean URLs, but for know i want to understand the basics :)

thx