Changes in engine noise on the approach are the norm going into to an airfield in a built up or mountainous area. Buildings and hills cause up and down-draughts on finals - quite often you experience an updraft and will have to take engine power off and adopt a slightly more nose down attitude, then once you've passed this, the downdraft will require another 'boost' of engine power.
The things you describe are nothing to worry about - very normal! I trained with lots of pilots who have gone to easy, BA and Ryanair and none of us use wildly different flying techniques. The amount of reverse thrust depends on runway length, where you want to exit the runway, and how long you have on turnaround for brake cooling. I fly into some airports with short landing distance where we try to get reverse thrust on ASAP, but sometimes it is not necessary due to long runways or at noise sensitive airports. Every single approach and landing is different due to the many variables.
I wouldn't worry about flying with Ryanair - the pilots out there, easy, BA, Ryanair and the rest all have to achieve the same licences and skill tests and are all trying to do the same job - get you on the ground safely!!