I was also in same state so let me clear your confusion.
You can make Einbürgerungsantrag if you have over 8yrs continuous stay and also employed only B1 required.
With Integrationskurs you can reduce this time limit to 7yrs but now the problem is if you already have B1 certificate then you may think why you need this Integrationskurs 660hrs class as it was same situation with me.So if you are staying here for long and also having B1 then the VHS may admit you for a 60hrs Orierntierungskurs which is a mandatory to attend even its a bit stupid as at the end its the same out of 250 questions they ask 25 questions.Now there is no shortcut and you have to attend this 60hrs and if you make a direct final test then the BMF don't issue the final Integrations certificate.So with your B1 and test result of Orientierungskurs along with the paper showing that you attended 60hrs Orientierungskurs(wichtig) you send to BAMF and get the Integrations certificate and get your einbürgerungs time reduced to 7yrs.
Now about Einbürgerungstest it is having exactly the same 250questions of Orientierungskurs plus 50 more but its entirely different test and this is something every person has to make egal you have passed Orientierungstest or not.So Orientierungskurs is only a preperatory test for Einbürgerungtest for those doing Integrationskurs and those over 8yrs don't need Integrationskurs don't need Orientierungstest but only Einbürgerungstest.
I hope now you are clear with your doubts