firstly sorry for my broken english,
i want to ask, if i use 2.11 ohm build on mech mod, using samsung 25r rated to have 20amp max output and lg hb6 which rated to be 40 amp max output, is it gonna be any difference in firing power?
Here's Mooch's test results on those batteries. The 25R will vape longer at 2500mah but has a lower current rating. Both those batteries are good choices for current rating, but you won't see a difference in vapor or hit strength between the two with a 2.11 ohm coil.
LG HB6 Pink 30A 1500mAh 18650 Bench Test Results...great 32A/1500mAh battery, better than ivory HB6
Samsung 25R New Green Wrap 20A (25R5) 2500mAh 18650 Bench Test Results...a great 20A cell
The current rating of a battery is a potential limit that indicates its ability to withstand the heat and current draw at max load without serious damage. A battery will only produce enough current (amperage) to service the load it's connected to. The advantage of a battery with a higher amp rating is that it isn't being stressed as much as one with a lower rating for a given load.
If the mech has a newly charged battery with a voltage at 4.2v, you'd be vaping at 2 amps and about 8.3 watts on that 2.11 ohm coil. That's in a safe range. The current and wattage would drift down to 1.5 amps and 4.9 watts by the time the battery drained to 3.2v.
If you want more "kick" from your mech, you lower the coil resistance. Just be careful to stay within safe ranges. Use the Ohms Law calculator at the link below to see how changing resistance affects current draw.
Ohms Law Calculator
If you are looking for more vape time on a charge, look for batteries with higher MAH ratings. If you want more control over your vape quality, buy a regulated mod that allows you to vary the voltage, wattage, and or temperature. You will be able to dial in the vape you like. A mech mod limits you to current battery voltage feeding a known resistance.