I need two join two traces of different widths, I use two different width at first place due to space constrains at some parts of the board. so what is the best method to do it elegantly and with no etching problems?
no etching problems?
If the smaller width works, this will also not be an etching issue. Also, this is a DC line, so you don't have to worry about anything geometrically here.
You're asking about æsthetics here. Well, can't help you with that, honestly, different people find different things pretty. It might be prettier to simply not have the thicker line extend this far up, so that the rounding doesn't extend beyond the upper edge of your thinner trace.
But honestly, go with what you layout software does.
As long as you obey the 'design rules' of your pcb supplier, you can do whatever you like with pcb trace width and not worry about 'etching problems'.
It's entirely normal to reduce the width of traces where space is limited. It's sometimes called 'necking'.
Remember that power traces usually need to be wider than others.
That aside, your board will likely appear 'neater' if you standardise on one trace width for signals.
There's no problem with manufacturing it as shown if the design rules are not violated.
It's aesthetically ugly, but it will work. Here is the more usual way of changing trace width in mid-trace in Altium:
By not changing the direction simultaneously with the trace width it is more pleasing to the eye, at least I think so.
Of course if you're running traces with controlled impedance or pairs with controlled differential impedance you have to be a bit more careful.