Hi there,
It is possible to change the finish of a 15 mm engineered flooring - wood floor sanding to remove the existing finish is required and a new finish is applied. If the product you have is 3-strip, I would believe this product has a 3mm top layer 'though, which does not change the situation, but such products can take restoration only once.
In your question about the finish... Oil-based products may be easier to maintain - in case of a scratch or wearing you can rub some oil with a cotton cloth on the floor and it will blend the damage.
Oils & Hardwax-oil are not hard-wearing sealants though. A better, requiring less maintenance finish is the varnish.
In short, the best advice for the durability of the finish is:
- Good hard-wearing products, such as "Bona Mega" or "Junckers Strong" or their 2-part, commercial-grade alternatives "Junckers HP Commercial" or "Bona Traffic HD". These in combination with Matt or UltraMatt sheens will give you good protection and make any future scuffs and scratches less visible.
- "Bona Naturale" - combines the best of all finishes, the highest durability, can be repaired (like oil), and natural matt sheen. The downside is cost - double the cost of some other finishes.