Welcome to the forum.
These are two very general broad questions you have asked here, the best advice I can give is to go and have a go and see what issues you hit (if any) likely issues for lanscape are going to be compositional, exposure of sky and depth of field. Similar with architecture if you are shooting from outside plus converging verticals.
Some snipptes of advice though:-
Before shooting both I would get familiar with AV (aperture priority) mode on your camera, setting exposure compensation and use a tripod if you have one if you don't then try and find some other means of keeping the camera still and stable.
Compostion wise look for foreground interest and think about how far into the distance you want the shot to be sharp if you want it to be sharp as far as possible then choose a high F number such as F16 and focus 1/3 in to the scene which should give you a sharp image back to front.
Read up about the rule of thirds there are plenty of articles about that google is you friend (you need to understand this rule before you can break it
) , if you want to get serious about landscapes then you will need to consider graduated filters or you may consider taking multiple exposures of a scene (i.e. 1 exposed for the sky and 1 exposed for the land) and combining them with software.
Another great bit of advice is to walk around the area to get a feel for it and try to imagine what it would be like at different times of the day and different weather conditions (so you may return another time). Also based on what you see think about what elements would make up your perfect shot at that scene for example slightly cloudy with light shining on that rock in the corner of the lake etc.
As I said earlier just have a go if you want feedback on your photos or advice then post on the forum that's why we are here.
Most important advice is keep yourself safe of course
I am sure others will be along to offer there great advice also.
Ohh and neraly forgot (bad me) take inspiration from others, look at the landscapes others have taken and work out what you like as that will give you a better understanding of what you are trying to achieve.