How hard? Go to your water suppliers website and get a report based on your postcode. Where I grew up it was 450+ ppm rA which is quite hard to work with. Here it ranges from 80-160ppm which is more straightforward. Treating brewing liquor is part of the game. Once you start doing it and relate the theoretical to the practical it gets quite straightforward.
Standard MO for me is a dash of metabisulphite to my hot liquor tank (area doesn't treat with chloramine) as I draw it fresh that day. Chlorine will gas off by allowing water to stand overnight, enhanced with agitation etc. Commercially it sits in a cold liquor tank, is used to chill wort and then sits in the hot liquor tank so gases off without treatment. 5-7ml of 80% lactic acid to reduce the rA depending on what I'm brewing and then another 3-4ml once topped up for the sparge depending on volumes gets me in a ball park. Salts are direct to the mash to give the desired sulphate and chloride concentration and to bring up calcium to 100-150ppm minimum with an eye to mash pH. For dark beers I don't acidify my water, tend to only bring sulphates up to 100ppm maximum for the extra calcium, rest has to come from chloride and I quite often use sodium carbonate direct to the mash at 1-1.5g per 10% of dark malts., also tend to split salts between mash and copper on dark beer depending on amount with an eye to mash pH. Don't even really need to test pH any more because it has gotten very routine over time. Use sulphuric and hydrochloric acid all the time at work, but not out of choice, just a legacy thing. Both contribute sulphate and chloride without calcium, so a bit of a bugger to build into something like a lager where you do not want significant sulphates, but still need a good chunk of calcium.
When you get really fussy you will want ideal mash pH (enzymatic efficiency, wort separation) ideal pre boil pH (prevent excessive phenol extraction) ideal post boil pH (fining, stability, calcium levels of the wort for yeast health going into fermentation) ideal post fermentation pH (flavour, clarity, stability, storage). You can start building sodium and magnesium salts in to recipes with a lot of extra pale/pislner malt to make up for the lower phosphates in these malts if you want a really sharp lager, but can't see why people need more than lactic acid, calcium carbonate, calcium sulphate and sodium carbonate (bicarbonate in a pinch), weird when I see brewers messing with magnesium salts (junk, 1/4th of the mEq compared to calcium equivalent) when not working in these specific situations.