Edge your lawn by digging a trench. The edges should be defined as perfectly straight or if you are doing curves, keep the radius consistent until you change directions. If you use a string and stake, the stake is the center of your circle. That radius stays the same until you have to move the stake either outside your lawn or back onto the lawn. Doesn't matter what what the radius of those circles are, they shouldn't be equal and large, sweeping arcs will look more natural. If you have your stake in the lawn, you paint your arc along that circumference until you have to place the stake outside the lawn and draw a new arc. Then you'll keep going back and forth, inside the lawn, outside the lawn until you've connected with where you started. It looks more professional that way. After you are satisfied with where you want your edge, stand on the lawn with a flat spade and cutting through the edge of the lawn dig down at an angle about 4-6". Throw the soil back up onto your beds, picking out chunks of lawn.
The only mulch I use for ornamental plant beds and lawns is human sludge mixed with sawdust and completely decomposed. You will have to call around to find who in your area makes this mulch. It is called different names, the one I used was called 'Gro-Co'. This mulch is beautiful, fine textured, no lumps, sticks, rocks, no pesticide residue, no weed seed!, smells wonderful. If not, find another supplier.
It is a dark taupe color and feeds your soil organisms. Your plants will look healthier than ever (usually one week and the difference is remarkable)! Put it on 2" thick. As with any mulch/soil, keep it away from the base of woody shrubs and trees. If you have any shallow-rooted plants such as azaleas, rhododendrons...daphne, only put down 1/2 - 1" of mulch within the plant's dripline.
This will kill most weeds and prevent any weed seeds from germinating. If a weed grows through or a seed blows on top to germinate, they are very easy to pull out. Don't use any other barriers beneath this mulch as you want the organisms in the soil to be able to eat this stuff. They then take it down into the soil and poop it out, aerating and mixing organic matter into the soil with no effort on your part. You won't need anything else except this trench, a line trimmer and this mulch to keep the grass from germinating or growing into your beds.
Every year or two you will need to replace this mulch. It is disappearing into your soil, improving it! Healthy soil, healthy plants, less water and few if any, weeds! How can you go wrong...you'll still need to fertilize, but not as much. If you are good with a line-trimmer you won't need to re-edge your lawn.
This mulch is also great for your lawn. My supplier could blow this stuff on beds/lawns and really saved a lot of work. Although I have to say this stuff is light and fluffy and easy to work with.
Can't use it for the vegetable garden, sadly, as it is a little higher in heavy metals. Hope this helps...I've done this not only for my yards but for hundreds, maybe thousands of client's yards. I won't use bark, wood chips...I tell my clients if they want that, they can find someone else. If they already have bark, they have to allow me to remove it, especially if someone's put plastic underneath! I usually remove the bark and transfer it to their green-belt area where it works fine under established, native plants.
I want my projects successful and clients happy. That is how good this mulch is and I haven't found anything better, yet. Maybe this will help you!