Is there any particular kind of assets for which you must have a will document or inheritance rules are sufficient?
There is nothing must. If there is no will Inheritance Rules will be applied. Although the rules may sound simple; the result could be very different from what you want. Some family member may want a different province rule to be applied; there could be disputes in the family; a stranger can claim to be partner ... even when things go fine; there is still a lengthy process to get a probate from court; establish the legal heirs and get the judgment.
It is always advisable to have a will as this will give out clearly how you want certain things to be dealt.
The will needs to be revised periodically to make it up to date with various events. Get a lawyer, as there would be certain items that would mean differently; for example if your spouse divorces you and marries someone else and dies before you; if you don't change the will; the funds still go to spouse and heirs determined or will left by spouse.
Can you create a will in such a way so that you can include all your current assets as well as any future assets which you may acquire after the will document was created?
Yes you can have the wording for example any future assets are to be divided equally between a, b and c. However it is advisable to redo the will when certain types of assets are acquired. For example an antique jewelry; items that can't be divided; can create dispute. Leave it to one and allocate more cash to others etc. Or clearly indicate this items needs to be sold in auction and cash divided.
Is inheritance rules sufficient for a family with average income with above scenario?
Inheritance rules are done as default allocation by the state to appear just. It is best to have a will.