If you want to find out how many version nodes you have you can run the following SQL query and check for the number of entries in the jcr:versioning workspace (replace JCR with the according schema):
SELECT JCR.ICMSTJCRWS.WSID AS WORKSPACE_ID, WSNAME AS WORKSPACE_NAME, COUNT(*) AS NODE_COUNT
FROM JCR.ICMSTJCRWSNODES, JCR.ICMSTJCRWS
WHERE JCR.ICMSTJCRWSNODES.WSID > 0 AND JCR.ICMSTJCRWS.WSID = JCR.ICMSTJCRWSNODES.WSID
GROUP BY JCR.ICMSTJCRWS.WSID, WSNAME
My recommendation is to only enable versioning for the design items and keep versioning set to manual for content items and site areas.