Hi lisiang.
Agree with the giving her a some sort of 'promise". But out of respect, you should maybe consult and ask for the parents permission first. Just my opinion. And of course try to save some "special privilege" until both of you are really married with a proper ceremony just to maintain the sparks until then. 2 years is actually quite a long period. But before that, you really need to sit down and discuss. ROM is a big thing. Is not a game. Once sign, not so easy to undo. So just sit, create some crisis and quarrel and see can your relationship sustain when in turmoil. Love is beautiful when is all new and sparkling. But once the spark is gone, then is more on responsibility and commitment. Is no game.
Just my 2 cents worth.
To choose a photographer you first need to allocated a budget. Then work on that budget. Don't just judge by the looking at their work online. Meet up and get to know them. Is not just about taking good artistic photos. Is about corporation, ethics and responsibility as well.
Just my personal opinion that I experienced myself. I regretted that I did not have a proper ROM photography and video and also a proper actual wedding day photography and video. What we did is trust our friends and family members to capture some photos and video for us. In the end, there is some photos. But mostly is the same group of people repeat and repeat. If you get what I mean. And we spend 3 to 4k on pre wedding photos and hack after three month I din't even know where is it now. Don't get me wrong, if you have the budget, there is no wrong to pay high price for Pre Wedding photo shoot. But just my personal opinion, I would put priority in ROM and Actual Wedding Day photography. Then later on, I would like to go for a Post Wedding Photo with our little baby. I think that would be more meaningful.
We ourselves are a photography studio and at the same time, a person who been through marriage before. So we might maybe understand some of our client situations.
Is very difficult or almost impossible to look for the perfect bridal house or a photographer. The best is just to minimize the risk of disappointments. For bridal house, just need to survey, compare, do it in writing, email with black and white. The problems with most bridal house is, they are mostly operated by sale person, not the owner them self. So they only have one thing in mind. Sales Sales Sales, Commission Commission Commission. So promised you with this with that, 2 month down the road, the sales person you dealt with, no longer there. So in the end no this no that. Oh and remember to demand first before signing. Not sign only demand.
For ROM or AD photographer, before engaging your photography service, just need to take some precaution. If possible, try looking for those licensed with proper company set up and organization. Easier to deal with if crap happened. Try avoiding freelancer unless your are really sure. Not that they are all bad in anyways. Even some of the famous ones are freelancer. But when a problem occurs, they might not have a strong back up from the company and consumer legal law protection.
Just my 2 cents worth... Cheers.

Parents permission are granted on my side but i dont think their side will be having any problem, anyhow after the proposal day i will talk to their parents because her parents are living quite far from me and her. *she is currently staying in my house together with my families*
err.... 'special privilege' apa ini?
Yeap, the ROM is big and significant enough for the rest of my lifetime and I am fully aware of it and decided after 5 years relationship with her. I have been experiencing the responsibility and commitment together with her these few years and i think we are ready for it.
So what do you suggest me to focus more on the ROM and AD photography and then a post wedding photography? How about those prewedding photography like those normally people done?
Thank you so much for da help.