I understand you being a bit nervous when it comes to terrain building. The tools are somewhat like coloring with fat crayons and trying to stay between the lines at the same time. There are ways around this fat-crayon approach using not just the tools we have built-in, but also digital Elevation maps, such as those available on the DLS or others that you can download and import into Trainz using TransDem (payware) or HOG (free).
Remember the baseboard grid has a 10 x 10 meter resolution by default. This is sometimes course but can be manipulated just the same. When I need to make slight changes, I find zooming out a bit and using a smallest-size cursor seems to help. Raising a road or track bed can be tricky, but I find if I raise the track or road then blend the terrain in around the grade, then things look better than trying to create a raised grade. The alternative lowering terrain on either side of the road or tracks works as well and I've done that too where I want the track to be graded. The difference is maybe 5 or 6 meters lowered and this makes the difference.
I noticed that you have TS12. If you are using this, there is also the 5 meter grid available. Just remember to create your 5 meter grid prior to texturing otherwise the textures can become weird. I made that mistake on my route, and I spend a long time retexturing the area again with limited success. The 5 meter-option is a bit hard to find. When creating a grid, you click on the screen a second time and the option comes up. This is only for that one baseboard and not subsequent baseboards which is weird.
To create landscapes and then put in tracks and roads, you can try displacement maps. These are grayscale images that provide height values that raise and lower the terrain with white being the highest and black the lowest on the 0-255 scale.
The final alternative is to use actual terrain from DEMs. This can be both frustrating and rewarding at the same time. The end result is a landscape based on the real thing which it is. There are resolution differences and you want to usually pull the medium-grade ones. The lowest resolution ones create really bumpy landscapes with exaggerated heights. The highest ones create truly awesome terrain, but you pay the price of more overhead. I won't go into details here. I'll let someone else explain this better than I can.
All I can say after all this, is experiment. There's no waste with virtual railroading and there's no mess either, so if you don't like something, try another method that works best for you.
John