As others have alluded, it depends...

A Plus fare (booked later in the day and then brought forward) would be a good bet - though a 90-minute connection time is highly unlikely to be enough to collect your bags and drop them at AMS.

I have done this and would have made 1h 40, but I was lucky and it was still tight (and the flight I wanted to change to was full anyway).

If you can afford to grab a one-way from AMS-LON then that's much better, especially as a Plus fare should give you the ability to change the flight even on the ground in LHR if needed.

On the outbound, however, I'd go the night before BOTH ways, without luggage, then drop my luggage off at LHR checking in as normal.