"Is inflation not a risk?"
Inflation is always a risk, but not because of the debt or deficit. Inflation with a fiat currency only occurs if the resources being purchased are scarce and only applies to those resources/goods, not the general economy or cost of living. If the economy is booming and the government creates money to purchase goods or labor the private sector is already using that spending will create inflation.
"Is too much national debt not bad?"
There is no national debt that taxpayers are responsible for. Simple dual entry spreadsheet accounting would show that a negative (debt) entry in one sector must create a positive (asset) entry in another sector and that negative and positive balance to zero when they get together in one sector. Government spending in the private sector is tracked by an entry labeled debt, but the spending is not reliant on actual Treasury debt.
Dollars are created by spending and destroyed by collecting them back via taxation, but the spending must be done first, so taxation is never a funding mechanism. Borrowing (Treasury debt) is simply a temporary tax that pays a small dividend upon a bond's maturity when the bond is recapitalized with interest, but is also not a funding mechanism as the dollars to purchase bonds must exist prior to the transaction It would be more accurate to state that spending "funds" borrowing (and taxation) than the reverse.
If the government balances its budget, clawing back a dollar for every dollar created/spent, nothing is left in the private sector to store the value of the spending transactions. In any other context that would be theft of the resources and labor the government uses. Leaving a portion of those dollars in the economy provides incentive for commerce and the necessary funds to retire private sector bank debt.
That means spending considerably more than is collected in taxes (deficit) and the debt is nothing more than a record of all deficit spending in our history, the net money supply. It is also the result of past productivity and not a mortgage on future productivity as most politicians would have you believe.
It is our national "savings" denominated in the currency Congress can create at will without restraint from revenue and represented in Treasury bonds because of a political decision, not necessity. As long as there are resources to be purchased, including any labor the private sector rejects, spending will not create inflation, even in the complete absence of taxation or Treasury debt.
The only way to pay off the debt is to recall all dollars ever created in taxation without creating more, leaving the economy with no currency and forcing default of all private debt. That is certainly not a goal we should aspire to.
