Without ORDER BY results can be different each time you execute (no guarantee).
If data is changing ORDER BY also can cause duplicates/skip, Also need to materialize all the qualified results (last one may be candidate first in order). This can cause higher latencies.
You mentioned queries are simple. See if you can use keyset pagination described Using OFFSET and Keyset in N1QL | The Couchbase Blog
If query using IntersectScan try to create composite index ( https://index-advisor.couchbase.com/indexadvisor/#1), if required provide USE INDEX hint.