With regards to stocking levels, and tank sizes, I would personally avoid that site like the plague. To listen to some of them one needs a 300 gallon tank for a shoal of 10 2" juvie CL's.
To the OP, a small group of 6 one inch CL's, and some cory cats, with adequate filtration, and regular weekly water changes, you should have no issues for the next 3 years. If you can upgrade sooner, great, if not it's not as though you will be stunting your loaches. If your situation changes down the road as previously stated larger clown loaches are always an easy sell.
FYI - I have seen CL's in very large well maintained tanks that were only 8" at 15 years of age. Not all CL's are genetically hard wired to reach 12+" in captivity. Generally there are always a few in each shoal that outgrow the rest. Some suspect that it's due to sex, with females growing faster, and overall larger than males. Whether that is true or not remains to be seen, but IME some CL's in each group do end up being smaller, and some larger.