All meters conform to a minimum standard and will do the job. Some are easier to use, some are smaller and so on.
4.6 is fine, in fact it is around the figure of a non diabetic. There are figures that are suggested as being as low as you should go, If you go below 4 or maybe 3.8 have a snack. It is unlikely that you will go Hypo, you are T2 and on Metformin only so should be OK.
Your liver will wake up and dump some sugar before you get much below 4.
Test 2 hours after any new food, once you know what you can and can't eat you can ease up on testing. Test your fasting BGs (when you first get up) maybe once or twice a month, there is not a lot you can do about them but it's good to know what's happening. If you feel unwell, test. Have a glass of whisky and test 1 hour later, Exclaim loudly "Now that is interesting!".
Keep a chart of what you eat and how your BGs respond, record any excercise and note what difference it makes to your BGs.
Take it along with you to the docs who should be mightily impressed especially if you throw in a graph or two. Except if he is like my doc. he will just ignore it and only look at the HbA1c results.
However, you will be able to see a trend, and if you do some simple maths you will be able to have a pretty good idea of what your HbA1c is likely to be.
Happy testing.
H