In the non canon Dragon Ball heroes game, there is a transformation called "Saiyan Beyond god" which is when you use god ki in base form (white/transparent ki) . This transformation is stronger than a SSJ, SSJ2, SSJ3, etc. Now the Dragon Ball heroes game is non canon, but this seems to fit with the idea from Dragon Ball Super / Resurrection of F, Goku in base form is able to fight 4th form Freezer, when Gohan super saiyan is defeated easily by Freezer 1st form. And later Goku mentions he can become a super saiyan god super saiyan because he is able to handle god ki and later transform into super saiyan. Does this mean he was using god ki when fighting Freezer 4th form, and that this base-looking form is stronger than turning into a regular super saiyan?
It was stated during the fight between Beerus and Goku that Goku had absorbed god ki into his base form which had indeed made him significantly stronger. Gohan, on the other hand, hadn't trained and his base form at the time was nowhere close to even teen Gohan who fought Cell. So his SSJ multiplier to his base form would've been very low. Freiza's first form was most likely stronger than Namek saga SSJ Goku. However, Goku has gotten substantially stronger since than and he was completely dominating the fight against final form Freiza who had gotten a lot stronger.
The Golden Freiza multiplier is a lot higher than the Super Saiyan Blue multiplier. This is why Golden Freiza was a lot stronger than Super Saiyan Blue Goku despite Goku's base form being a lot stronger than Freiza.
About the transformation Saiyan Beyond God, it seems to be a possible way to using a new form of ki. The divine ki who Goku has acquired by fighting Beerus.
Saiyans can use this ki rather than theirs to turn into a Super Saiyan form.
This is visible by the blue hair color instead of the golden yellow classic color also this ki seems to be stronger than the saiyans base form ki because Goku is weaker than Beerus when he is into his base form.
So we can say using divine ki is stronger than using saiyan's base form ki.